Britain has warned the EU must reform itself or slide into irrelevance in the face of emerging powers such as China and India.
British Finance Minister George Osborne said on Wednesday that without such change, the UK could leave the bloc.
“In Europe but not run by Europe. That’s the phrase that sums it all up for me, now we have the chance to give the British people a real choice.”
Prime Minister David Cameron’s Conservative party has promised a referendum on staying in Europe in 2017 if it wins the next election.
Many say the move has been inspired by the rise of the UK Independence Party.
“I find it’s very unfortunate and rather dangerous for Britain, if mainstream politicians, namely those of the Conservative party, go after their extreme-right-wing, anti-European agenda,” said Ana Gomes, a Portuguese Socialist MEP.
The British government has also raised the possibility of restricting some EU nationals’ right to work and settle in the UK, with a view to tackling so-called welfare tourism.
A British government report on free movement in the EU, set to be released shortly, has been delayed until possibly after May’s European elections.