Dozens of MPs are planning to defy the government and vote in favour of a referendum on leaving the EU.
A eurosceptic rebellion grew on Thursday with a further 18 MPs signing a backbench motion calling on the government to hold a referendum on Britain’s membership, bringing the total to 76.
Ministerial aide Stewart Jackson became the first member of the government to say he was willing to resign in order to vote Yes in Monday’s Commons poll.
‘I will vote in favour of the motion and, in so doing so, I will very likely relinquish my position as parliamentary private secretary to the Secretary of State for Northern Ireland,’ he told BBC Radio 4.
Other ministerial secretaries are thought to have made an agreement to do the same if the government whips the vote, to make government members toe the coalition line. It is potentially the biggest rebellion to have faced Mr Cameron in his premiership.
Downing Street is planning to put a three-line whip on the vote but could declare it a ‘free vote’ or a ‘one-line whip’, meaning MPs could vote with their consciences without having to resign.
However, the rebellion is unlikely to succeed as Labour leader Ed Miliband said he will push his MPs to vote with the government on the issue.
He accused the prime minister of failing to control backbench MPs, adding: ‘ David Cameron should show some leadership. He should not be spending the next few days negotiating with his backbenchers but negotiating for Britain to sort out the eurozone crisis.’
Mr Cameron said it was the wrong time for a referendum ‘when we have so much to do to get Europe to sort its problems out’.