Liberal Democrats are “pro-referendum” on Europe

Liberal leader Nick Clegg is under pressure to back the Conservatives' referendum on Europe. PA

Nick Clegg is reported to be under pressure from ministerial colleagues to match David Cameron’s commitment to hold an in/out referendum, but the Lib Dems said there had been no change in the party’s position, with the prospect of a public vote on severing ties with Brussels only if there is a proposal for a significant transfer of powers.

But the source would not say whether Lib Dem MPs would be ordered to vote for or against the latest Tory attempt to legislate for a referendum by the end of 2017, stating “we will cross that bridge when we come to it”.

Tory former minister Bob Neill will launch a fresh attempt to get a referendum bill through Parliament after legislation proposed by colleague James Wharton collapsed in January in the face of Labour and Liberal Democrat opposition in the Lords.

The Prime Minister has said he is ready to invoke the Parliament Act to force through referendum legislation but for that to apply, a bill identical to that proposed by Mr Wharton would have to pass the Commons without any amendments - which may prove difficult to achieve.

The Lib Dems and Labour abstained in the Commons on Mr Wharton’s bill, leaving their peers to block its progress.

Asked how the party’s MPs would respond to Mr Neill’s bill, a source close to the Deputy Prime Minister said: “We will cross that bridge when we come to it. There is a long way to go before that.”

Reports in The Times and Daily Mail suggested Mr Clegg was under pressure to match the Tory commitment to a referendum in the wake of the electoral mauling the Lib Dems received in last month’s European Parliament contests, which left the party with a single MEP.

But the source played down the prospect of a change in the Lib Dem stance: “There has been no change in our position. We are unequivocally a pro-referendum party, we believe British people should get a say on staying in Europe.

“We have gone much further than any government in legislating for a referendum.”

The source said Mr Clegg believed the referendum “should take place at a time that’s right for the country” rather than on an arbitrary timescale designed to appease a “divided Tory party”.