Launching his party's manifesto yesterday (13 April) with a pledge to return power to the people, Tory leader David Cameron vowed to hold referenda on all future EU treaties that transfer power from the UK to Brussels.
But the Conservatives stopped short of promising to re-address Britain's ratification of the Lisbon Treaty, which was completed in July 2008.
"We will work constructively with the EU, but we will not hand over any more areas of power and we will never join the euro," the Tories' manifesto states, adding that Britain's best interests are served by membership of a Union that is "an association of its member states".
The Tories describe rivals Labour's ratification of Lisbon without holding a referendum as "a betrayal of this country's democratic tradition" and pledge in their manifesto - unveiled at London's Battersea Power Station - "to make sure this shameful episode can never happen again".
Gordon Brown's Labour, meanwhile, warned that "sullen resistance and disengagement achieve nothing" and expressed pride that the UK "is once again a leading player in Europe".
"The poverty of the Tory vision is summed up by their false choice between an alliance with the United States and one with Europe. In Europe they are not just isolated, but marginalised, in a tiny group of far-right parties that endorses extreme views and is stuck in climate-change denial," reads their manifesto, launched by Prime Minister Brown at Birmingham's Queen Elisabeth hospital on Monday.
'Referendum lock'
"We will ensure that by law no future government can hand over areas of power to the EU or join the euro without a referendum of the British people," reads the Conservative manifesto, which includes a pledge to "amend the 1972 European Communities Act" so that any future treaties that transfer powers to Brussels "would be subject to a referendum – a 'referendum lock'".
Vowing never to take the UK into the EU's single currency, the Tory manifesto stresses that "our amendment to the 1972 act will prevent any future government from doing so without a referendum".
"The steady and unaccountable intrusion of the European Union into almost every aspect of our lives has gone too far," reads the document.
Rivals Labour, meanwhile, will seek to "lead the agenda for an outward-facing European Union that delivers jobs, prosperity and global influence".
"Our belief is that Britain is stronger in the world when the European Union is strong, and that Britain succeeds when it leads in Europe and sets the agenda for change," reads their manifesto.
Lisbon's 'ratchet clauses'
The Conservatives warned that the Lisbon Treaty contains "ratchet clauses" allowing the EU's powers to expand in future without requiring a new treaty, and cited the potential establishment of a European Public Prosecutor's Office as an example.
Any major transfers of power via such clauses would be subject to referenda, the Tories said, pledging never to allow a future EU public prosecutor any jurisdiction over the UK.
The Tories also pledged to return key powers over legal rights, criminal justice and employment legislation from Brussels to the UK.
Labour categorically ruled out any such possibility, stating in their manifesto that "we reject any attempt to renegotiate or unravel social rights for the British people".
"Economic strength and social protection go hand-in-hand – a modern EU must enhance competitiveness and growth while guaranteeing security and fair rights at work," reads their manifesto.
On enlargement, the Conservatives will "press to keep the EU's doors open to those countries, including Turkey, that wish to join, conditional on the rigorous application of the accession criteria".
Labour also supported Turkey's accession bid and called for all Western Balkan states to open negotiations on EU membership by 2014.
Meanwhile, Britain's third biggest party, the Liberal Democrats, launched their manifesto this morning with a commitment to holding "an in/out referendum [on EU membership] the next time a British government signs up for fundamental change in the relationship between the UK and the EU".
Power to the people
Domestic headlines focused on the Conservatives' pledge to return power to the people of Britain. Parents would be allowed to run their own schools, local residents would be able to elect their own police chiefs and voters would be able to sack poorly performing MPs.
Their manifesto, which bears the title 'Invitation to join the government of Britain', includes an offer to hold local referenda on any issue if 5% of residents were to back it.
"Everyone is going to have to get involved" in solving the UK's problems as government cannot do so alone, said Cameron at yesterday's manifesto launch, calling for the establishment of "the Big Society".
Meanwhile the UK Independence Party pledged in its manifesto not to field candidates against any "committed Eurosceptic" from other parties, including six Tories.
