According to European rules on the free movement of goods and people, EU citizens can move freely between member countries and apply for jobs without having to produce special work permits.
However, public opinion appears divided over the merits of free movement, with several EU countries currently debating whether this has led to "social tourism" or "benefit tourism".
In spring, 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.
In January, the EU labour market will be fully opened to citizens of Bulgaria and Romania, which joined the EU in 2007, fueling concerns in the UK and other countries about a surge of immigration from those countries.
But a new report by the consultancy firm ICF-GHK for the Commission says that an overwhelming majority of those who move from one EU country to another do it for work and not to receive social benefits.
In most countries, EU migrants represent less than 5% of welfare beneficiaries. And the European Commission argues that these migrants make an overall net contribution to the finances of their host countries because they pay more in taxes than they receive in benefits.
When it comes to healthcare, unemployed EU migrants on average only cost 0.2% of the overall health budget, according to the study.
In Cyprus for example, the estimated healthcare spending on non-active EU migrants stands at between 2.9% and 3.9% of total health spending. Average spending is similarly low in other countries such as Ireland (1.8-2.3%), the UK (0.7-1.1%) and Denmark (0.2-0.7%).
The authors cautioned however that due to the quality of official data on non-active migrants, those figures should be considered as estimates.
Benefiting from migration
Jonathan Todd, a spokesperson at the EU Commission, told the BBC that the report showed that EU countries' welfare systems were actually benefiting from migration.
Sweden's Labour Minister Elisabeth Svantesson said EU migrants often had better employment rates than native citizens. The highest numbers of non-active EU migrants, per head of population, are in Luxembourg (13.9%), Cyprus (4.1%), Belgium (3%) and the Republic of Ireland (3%).
The report said that more than two-thirds of the non-active EU migrants are students, jobseekers and pensioners, rather than migrants' relatives.
"We don't see social tourism in Sweden," Svantesson told Sweden's Radio. "It looks as if what we see in this report is actually that EU migrants contribute to the countries they travel to. This is exactly what's behind the 'free movement' thought - that it should benefit both the individual and the EU countries," the minister continued.
A similar report, commissioned by the UK Foreign Office and published in April, came to similar conclusions, and challenged claims by Prime Minister David Cameron that Britain faces a massive wave of immigration from Bulgaria and Romania when labour restrictions applying to these countries are lifted next January.