High unemployment in southern Europe is helping to fuel migration to Britain from other EU nations, experts at Oxford University said on Wednesday.
Spain, Portugal and Italy - three of the top six countries for EU migrants to Britain - had recent unemployment rates of 25 per cent, 14 per cent and 13 per cent, respectively, a report by Oxford's Migration Observatory said.
"There is no one single 'pull' factor that attracts migrants from the EU to the UK, but a combination of economic and social factors does appear to have made the UK an attractive destination," the report said.
It noted that "record high employment rates and low unemployment in the UK contrast with continued weak labour market conditions in some eurozone countries, such as Spain."
Some 137,000 Spanish people - more than double the 2011 total - were among the 3.3 million citizens of other EU countries who were registered in Britain last year.
The number of Italians rose by 50,000 to 176,000 in the same period, the report said, while Poland remained the top source nation of EU migrants with 818,000 citizens registered in Britain.
"Job growth in the UK and the strength of the economic recovery in southern European countries in the short to medium term ... are likely to influence the pressure for EU citizens to migrate to the UK," it said.
Campaigners for Britain to Leave the European Union in an in-out referendum set for June 23 have claimed that migrants from within the bloc put a strain on the country's benefits systems and job market.
In another report published on Wednesday, the Open Europe think tank examined the potential impact of a British exit from the EU, or Brexit, concluding that EU migration would be "unlikely to reduce much."
Open Europe, like the anti-EU UK Independence Party, wants Britain to adopt an Australian-style, points-based immigration system that favours people with professional skills.
If Britain leaves the EU there is likely to be "a trade-off between the depth of any new economic agreement with the EU and the extent to which the UK will have to accept EU free movement," it said.
"The evidence from the precedents of Norway and Switzerland suggest that the deeper the agreement, the more likely the UK will need to accept free movement," Open Europe said, adding that a British points-based system might have to include preferential treatment for EU citizens.