Up to 50 Tory rebels are expected to formally reject David Cameron’s EU renegotiation plans today and declare that Britain should leave the European Union.

In a major challenge to the Prime Minister, members of the Conservatives’ Eurosceptic group in Parliament will reject his ‘feeble’ renegotiation plans.

As many as 50 MPs, MEPs and Peers from Conservatives for Britain could ditch their formal neutrality and actively call for a vote to leave.

Under fire: Momentum is building against David Cameron as Eurosceptics say his renegotiation plans for the EU are 'feeble' and as many as 50 MPs, MEPs and Peers could call for a vote to leave

Mr Cameron set out his formal negotiating position last week, highlighting what he hopes to secure from other European Union leaders ahead of an in-out referendum by the end of 2017.

His plans, which were set out in a letter to Donald Tusk, the president of the European Council, were widely derided for revealing that he had appeared to back away from the intention to prevent migrants from claiming benefits for four years after they arrive in this country.

Steve Baker, the Tory MP for Wycombe, and MEP David Campbell Bannerman, who are co-chairmen of Conservatives for Britain, will put a formal proposal for Britain to leave the EU before members of the group at a meeting today.

They are due to set out a series of ways in which Britain’s relationship with Brussels should be fundamentally changed.

They will say that migration policy should be made by the Government and be based on UK citizenship, not European Union citizenship.

They also want an end to the supremacy of EU law over UK law – that Parliament is ‘transparently accountable’ to the British people for all of the laws of the country.

Let's get out: Steve Baker, the Tory MP for Wycombe, says the Prime Minister's proposals for reforms will not satisfy the British people

And they say Britain should conclude its own trade deals, and control the amount of money we send overseas, instead of having it set by Brussels.

Speaking to the Daily Mail last night, Mr Baker said: ‘The Government’s negotiating objectives would leave the EU substantially unreformed.

‘Our relationship with it would be fundamentally unchanged. That is why I am asking Conservative MPs to join me in campaigning to vote leave and take control of our future.’

Mr Campbell Bannerman said the letter to Mr Tusk was ‘very disappointing’ and the PM’s goals were ‘feeble’. He added: ‘It has made the renegotiation irrelevant. Even if the Prime Minister achieved everything, it is not the fundamental reform or change we were looking for. It is not going to satify us nor will it satisfy the British people.’

Slapped down: Downing Street has reacted to Mayor of London Boris Johnson's challenge that Parliament should overturn European directives it disagreed with

Conservatives for Britain will still formally remain neutral, as several leading members have yet to take a position on the renegotiation. But significant numbers of individual MPs, peers and MEPs are expected to take a formal position on a Brexit – or a British exit for the EU – over the coming months.

Details of the move emerged as Downing Street slapped down Boris Johnson’s call for MPs to be given an emergency veto over EU laws.

In a clear challenge to the PM, the Mayor of London said on Sunday that Parliament should be given the power to overturn any European Union regulations and directives it disagreed with.

Asked yesterday whether Mr Cameron agreed with Mr Johnson, the Prime Minister’s spokesman said: ‘That’s not part of our negotiation.’