By Kylie MacLellan
LONDON (Reuters) - The number of EU citizens moving to Britain rose 27 percent in 2013, an awkward statistic for Prime Minister David Cameron on the day Britons voted in European elections that an anti-immigration party looks set to win.
Immigration has joined the economy at the top of voter concerns, fuelling the rise of the UK Independence Party (UKIP), which wants Britain to leave the European Union.
It is expected to top the poll in Britain, ahead of the opposition Labour party and Cameron's Conservatives, when results are announced on Sunday - part of a marathon election taking place across the 28-nation EU.
The Office for National Statistics (ONS) said on Thursday that the overall net inflow of long-term migrants to Britain rose to 212,000 last year from 177,000 in 2012. More than half a million arrived to live in the UK, compared with 314,000 who left.
Cameron wants to cut immigration, but cannot control numbers arriving from Europe because EU citizens have the right to live and work anywhere in the bloc - a fact UKIP cites as a key argument for Britain to pull out.
Opposition parties latched on to the figures, with Labour saying the government's immigration pledge was "in shreds".
UKIP leader Nigel Farage said: "We simply cannot go on like this if we are to even begin the task of restoring the living standards and community cohesion available to millions of hardworking British families. Enough's enough."
Polls suggest many people are concerned that immigrants are taking the jobs of British workers and straining public services like housing, health and education, though data suggest they are actually much less likely than locals to make claims on the welfare state. The government set out new rules earlier this year to limit EU migrants' access to benefits.
Immigration and Security Minister James Brokenshire said: "We are focusing on cutting out the abuse of free movement between EU member states and addressing the factors that drive European immigration to Britain."
While the number of non-EU arrivals was down slightly, the ONS said 201,000 EU citizens came to live in Britain in 2013, up from 158,000 the previous year. Of those, 125,000 immigrated for work.
The number from Bulgaria and Romania - the EU's newest members, which joined in 2007 - rose to 23,000 last year, from 9,000 in 2012, the data showed. From the start of this year, citizens of those countries were entitled to take jobs in Britain or other member states without a work permit.
The rise in UKIP's popularity has increased pressure on Cameron's Conservatives to get tougher on immigration. He has pledged to cut net migration to below 100,000 a year, but his promise has so far been undermined by figures consistently heading in the opposite direction.
In an interview with Sky News on Sunday Cameron declined to comment on whether the government was sticking to its commitment, saying only that it was "working towards" the target. If he wins a general election next year, he has promised voters a referendum by the end of 2017 on whether to stay in the EU or leave.
(Editing by Mark Trevelyan)