British Prime Minister David Cameron is bracing for a fresh Conservative rebellion over Europe this week as about 100 of his party's lawmakers look set to defy him in a parliamentary vote.

Tory divisions over Britain's membership of the European Union, never far below the surface, have burst out into the open once again ahead of the expected vote on Wednesday.

Eurosceptic MP John Baron has tabled a non-binding motion expressing "regret" that last week's Queen's Speech, which set out the government priorities for the year, did not include a promise to legislate for a referendum on EU membership.

Cameron has promised to hold a referendum if his party wins a majority at the next general election in 2015. Currently the Tories share power with the smaller pro-EU Liberal Democrats.

Media reports suggest 100 lawmakers are likely to support Baron's motion, a third of the parliamentary Tory party and an increase on the 81 Tory MPs who demanded a referendum in a 2011 vote.

Cameron's office has said he is "relaxed" about next week's vote, but it emerged this weekend that ministers have been told they cannot support Baron's amendment and should abstain.

It would be unprecedented for ministers to vote against their own government's Queen's Speech. But many eurosceptics in the cabinet would also likely refuse to openly condemn a motion which reflects their own views.

Amid front-page newspaper headlines proclaiming "Tory civil war" and "Tories in Europe turmoil", senior Conservative ministers took to the airwaves on Sunday to try to calm the storm.

"You can't have a civil war when everyone is on the same side," said Education Secretary Michael Gove.

He said the "overwhelming majority" of Tory MPs wanted a different relationship with Brussels, and admitted that he believed leaving the EU would be "perfectly tolerable".

But Gove said the rebels simply "want to let off steam" and insisted Cameron's promise to renegotiate Britain's terms before putting them to a vote in 2017 was the right approach.

However, Baron wrote in the Sunday Telegraph that the prime minister's pledge "is not yet believable".

He said legislating for a referendum "would put this right" and vowed in the coming weeks to seek "every means possible to bring legislation to parliament".

Home Secretary Theresa May and Defence Secretary Philip Hammond also backed the prime minister's plans in television interviews and confirmed they would abstain in next week's vote.

May said she had "every sympathy" with the rebels but added: "I don't think it's right for ministers to effectively vote against the programme we put forward in the Queen's Speech."

Hammond was asked if he shouldn't therefore vote against Baron's motion, and for the Queen's Speech.

"I wouldn't want to vote against it and allow that to be misinterpreted as in any way questioning our commitment to, our belief in, the idea of a referendum," he said.