In the upcoming election campaign, the debate over the EU will be dominated by the question of an in/out referendum and the issue of immigration.
EURACTIV asked UK-based think tanks to analyse the policy implications of the European positions held by the main political parties.
In/out referendum on EU membership
The UK entered the EEC in 1973 after a referendum returned a result of 67% in favour. But it did not hold a referendum on any of the subsequent major EU treaty modifications, whether in Maastricht (1992), Amsterdam (1999) or Lisbon (2009).
The 2011 European Union Act was designed to remedy this. Now, a referendum will have to be held on any future EU treaty change transferring additional powers from London to Brussels.
In January 2013, Prime Minister David Cameron promised to hold an in/out referendum on EU membership by 2017 if the Conservatives win the next election. The vote will take place after renegotiation of the terms of membership and a "new settlement" on membership for the UK is reached.
Cameron was widely believed to have offered the vote to appease the Eurosceptic wing of the Conservative Party and to fend off the rise of the UK Independence Party. Neither appears to have been successful, and the announcement ignited debate about the reforms the UK should pursue in Europe.
The issue of a referendum will be a constant presence during the election campaign, with the Tories seeing it as a major vote winner for their party.
>> Read: Two years after Cameron's EU speech: Is Britain closer to leaving?
Sunder Katwala, of British Future, a non-partisan think tank, says the EU has a long history of dividing the Conservatives. He says the party "is now united around offering an in/out referendum, though significant sections of it will find themselves in different camps once that question is put".
As for the Labour Party, its position of not holding a referendum unless a significant transfer of powers takes place from London to Brussels "has won the party friends in the business community who fear the uncertainty a referendum would bring", Katwala said. "UKIP's call for a referendum has increasingly centred on the issue of migration," says Katwala, which is "the issue that matters most to UKIP voters".
The Tories have said they will hold a referendum by 2017 at the latest if returned to government. There have been recent calls to bring this date forward. Katwala says such a move would limit both sides' ability to hone a message that reaches out beyond their base support. "The EU referendum will be decided by voters who don’t think or care too much about Europe."
"Whether Britain remains in the European Union could well be the biggest issue of the next Parliament. But it will have a lower profile in this election, where the parties will argue mainly over the merits of holding a referendum."
Institutional reform: Giving national Parliaments a greater say
Last May, the pledge rang out across Europe, "This time is different". A year on, the question remains - was it? Turnout was an all time low of 43%. In the UK, it was even lower: 34%.
This has raised questions over the democratic deficit of the EU, and the extent to which the EU makes rules in areas in which it has little accountability.
Debates surrounding a federalist-like integration of the eurozone in the wake of the sovereign debt crisis has raised fears in Britain that so-called "euro-in" countries will club together to push their own agenda, leaving the "euro-outs", such as Britain and Denmark, on the sidelines. Other institutional debates, such as the removal of the European Parliament's Strasbourg seat in favour of a single one in Brussels, are also popular in the UK and stir endless media controversy.
But with major EU institutional changes still fresh from the adoption of the Lisbon Treaty, which entered into force in 2009, there is little appetite for another round of institutional negotiations.
A greater role for national parliaments may prove popular around the EU, according to Agata Gosty?ska, a Research Fellow in EU Institutions at the Centre for European Reform (CER), a pro-European think tank. But gaining support in Brussels may be more difficult, she says.
“The Commission will be hesitant to support the idea of granting parliaments veto rights on legislative proposals," she said referring to British calls for a 'red-card' system allowing EU countries to veto proposed legislation. "The European Parliament, which still treats [national] parliaments as its rivals rather than allies, will oppose it too," she predicts.
While the principle might be of interest to the most eurosceptic member states, formal agreement on a red-card principle would in any case require a treaty change. Any such move would be highly unpopular everywhere except the UK, because the unanimity rule would almost certainly bring EU institutions to a standstill.
Instead of such blunt instruments, Gosty?ska argues there is scope for more parliamentary scrutiny of the government's actions at EU level, within the existing treaties.
“British MPs often complain the government does not share all the relevant documents with them. Some MPs would also like to have more regular parliamentary debates ahead of the European Council [of EU heads of states]. The reform of the British parliamentary scrutiny practice could boost parliamentarians’ interest in EU affairs and facilitate their greater involvement in the EU decision making process.”
Eurosceptics are also in for bitter disillusionment on the single seat campaign for the European Parliament, where their interests match those of EU federalists. Despite widespread support in the UK, Gosty?ska says agreements on the issue remains highly unlikely.
Indeed, when it comes to treaty change, unanimity is required and Paris will not doubt wield its veto. “France is vitally interested in keeping Strasbourg as one of the Parliament’s seats and will oppose any attempts to move plenary sessions to Brussels,” she says.
In addition, the Conservatives are likely to campaign for limiting the jurisdiction of the European Court of Human Rights, which many in the party see as encroaching on British sovereignty. Home Secretary Theresa May said Britain should consider leaving the European Convention on Human Rights, because it interferes with the government's ability to fight crime and control immigration.
"Despite not being an EU institution, it is linked to the wider Europe question by much of the electorate,” says Pawel Swidlicki a Policy Analyst at Open Europe, a euro-critical think tank.
Economic reforms and trade
The EU has long been considered in the UK as an overbearing influence, with many arguing that the benefits of the EU single market for goods and services are drowned out by excessive red tape and regulation (even if the British press is keen on making them up).
The Conservative Prime Minister, David Cameron, said the EU had become "out of touch" with its citizens, with "pointless rules and regulations that stifle growth, not unleash it". He said Britain should use the eurozone sovereign debt crisis as an opportunity to re-shape the Union as a network rather than a bloc. Britain, he continued, should seize the opportunity "for powers to ebb back instead of flow away" from national governments.
The UK would seek EU opt-outs on directives affecting labour rights and financial services regulation if eurozone countries adopt fundamental treaty changes, Cameron told the UK Parliament in 2011.
Cameron believes he can win backing from Germany, which also wants economic and institutional reforms, although for different reasons. During the eurozone crisis, Berlin has repeatedly called for changes in EU treaties, needed to strengthen the economic governance inside the eurozone.
Following the eurozone crisis, a key priority of the new Junker Commission is to boost the economic performance of the EU. First Vice-President, Frans Timmermans, has been given the task of reducing red tape, including a review of proposals by the previous Commission yet to be enacted, a move widely seen as a victory for Cameron's campaign to make the EU more efficient.
But the Juncker reforms have not yet convinced British politicians, who tend to judge the EU's performance solely by its ability to generate economic growth. At the same time, most of them are wary that reforms to boost political and economic integration in the eurozone will create a two-tiered Europe, leaving Britain on the sidelines.
Trade is another area where Britain has traditionally had strong interests. However, while the UK is a big supporter of free trade, there are widespread concerns that the EU-US trade agreement, TTIP, will negatively impact on the National Health Service, described by former chancellor of the Exchequer Nigel Lawson as "the closet thing the English have to a religion".
According to Swidlicki there are a host of economic reforms that, although facing resistance in some member states, have cross party support in the UK such as "the need to make the EU more dynamic and economically competitive" and the prevention of eurozone members dominating the single market.
"Key reforms are likely to include an aggressive drive to cut EU red tape, to reform and re-focus the EU budget, to properly open the EU market for services and to complete the TTIP free trade deal with the US."
Sunder Katwala says of all those issues, TTIP is likely to prove the most controversial. The Green Party will seek to raise the profile of TTIP negotiations as it seeks differentiation between itself and the other parties (The Greens oppose TTIP), but Katwala warns, "It is currently an issue much better known to activists than voters."
Immigration: Putting the brakes
At the last election, David Cameron said he would reduce net immigration down to the tens of thousands per year "no ifs, no buts."
The latest figures show net immigration to the UK 298,000 - 54,000 higher than it was when David Cameron came to power in 2010. The Conservatives blame a lack of control over EU migration and have said they want to curb EU immigration if reelected in a May 2015 general election.
In January 2014, the EU labour market was fully opened to citizens from Bulgaria and Romania, which joined the EU in 2007, fueling concerns in the UK and other countries about a surge of immigration from Eastern Europe.
In a major speech made last November, Cameron said the EU should change its rules on immigration, warning he would “rule nothing out" including campaigning to leave the Union if Britain's concerns fall on deaf ears.
Eurosceptics want to stop what they regard as welfare abuse by immigrants who are putting pressure on local services, such as health and housing, without having paid into the system through taxes.
Public opinion appears divided over the merits of free movement, with several EU countries currently debating whether this has led to "benefit tourism".
In 2013, the interior ministers of the UK, Germany, the Netherlands and Austria sent a letter to the European Commission warning that some cities had come under considerable strain from EU migrants claiming welfare benefits.
However, proposals for a cap on immigration provoked strong warnings from the European Commission, which regards freedom of movement with the EU as sacrosanct.
>> Read: 'Benefits tourism' in the EU is a myth, report says
Introducing restrictions on the principle of free-movement, Swidlicki points out, is something neither Switzerland or Norway have achieved. "Although the proposals set out by David Cameron are more far-reaching than similar proposals set out by Labour and the Liberal Democrats they all agree on this basic principle," says Swidlicki.
"These will require changes to EU laws backed by a majority of member states which again will prove challenging, but since it would keep in place the principle of free movement itself, a compromise should be achievable.”
Such compromises may well involve limiting access to the benefit system for new migrants says Camino Mortera-Martinez, Research Fellow in Justice and Home Affairs at the Centre for European Reform.
“Germany is already discussing a law to limit the time that EU citizens can stay in the country looking for a job, which is very much in line with Cameron’s approach to EU job-seekers. However, any reforms would still meet the resistance of the European Parliament and the European Commission.”
Home affairs, security and defence
The ruling Conservative party had initially warned that Britain would opt-out from all EU matters related to Justice and Home Affairs (JHA). Since the 2009 adoption of the Lisbon Treaty, those matters - where Britain used to have a veto - are now subject to qualified majority voting in the Council, with the European Parliament now upgraded to a full co-legislator role.
Britain, which does not participate fully in the implementation of certain JHA measures, threatened to opt-out entirely from EU cooperation on police and criminal matters, saying it wanted to regain its national sovereignty on those matters.
UK sources said Britain had problems with the European arrest warrant, the Schengen Information System, and some EU agencies such as Europol, Eurojust, along with a few others.
The Centre for European Reform, a British think tank, warned the decision would have "major implications" for Britain's security as the opt-out would make it more difficult for British police to conduct international investigations and convict criminals abroad.
These warnings have not gone unheard. At the end of 2014, the UK opted out and then immediately back again into 35 Justice and Home Affairs measure, including the European Arrest Warrant, Europol and Eurojust.
Camino Mortera-Martinez, a research fellow on justice and home affairs at the Centre for European Reform (CER), says the debate has now moved on.
“Even the Conservatives seem to be aware of the importance of police and judicial co-operation to fight cross-border crime," she says. However, there is a growing exhaustion towards the British 'pick and choose' approach to judicial cooperation.
After the January 2015 terrorist attacks in Paris, the current tendency seems to be more intelligence sharing, not less, said Mortera-Martinez. "UKIP’s argument on damaging the special relationship of the UK with the US is not likely to be accepted by other European actors, who value the UK’s leading role in the fight against international crime,” she said.
Earlier this year the President of the European Commission, Jean-Claude Juncker, reiterated his desire for an EU army. The call was resolutely rejected in the UK.
>> Read: Juncker: NATO is not enough, EU needs an army