Downing Street has launched a major investigation into alleged links between foreign governments and the MPs behind the 'Surrender Act' which could force Boris Johnson to delay Brexit, The Mail on Sunday can reveal.

Sources said No 10 took the unprecedented action after officials received intelligence that the MPs, including former Cabinet Minister Oliver Letwin, had received help drafting the Bill from members of the French Government and the European Union.

This newspaper has also learned that the rebel MPs have drawn up plans for a second Act which would allow Commons Speaker John Bercow to bypass the Prime Minister if he cannot strike a deal to leave the EU on October 31.

The new law would allow Mr Bercow to personally ask Brussels for a further delay on behalf of the Commons.

This newspaper has also learned that the rebel MPs have drawn up plans for a second Act which would allow Commons Speaker John Bercow (pictured) to bypass the Prime Minister if he cannot strike a deal to leave the EU on October 31

But last night No 10 hit back amid claims from senior sources that Mr Letwin (pictured) had agreed the January 31 date in the first Benn Act with figures at the French Embassy in London

The rebels have even discussed using the legislation to give Mr Bercow the power to appoint a new British commissioner to the EU, with pro-Remain former Home Secretary Amber Rudd mentioned as a candidate.

The Benn Act, passed earlier this month and controversially dubbed the 'Surrender Act' by No 10, states that if Mr Johnson fails to win a deal by the end of the next EU summit on October 18, he must write a letter to Brussels asking for the UK's departure to be delayed until January 31 – something which he says he will refuse to do.

Under the rebel plan, the Commons would sit on October 19 – the first Saturday sitting since the Falklands War in 1982 – to pass a new Bill giving Mr Bercow the power to write the letter. A senior Commons source said: 'The rebels say that, if Boris wants to play with nuclear weapons, then so will they'.

But last night No 10 hit back amid claims from senior sources that Mr Letwin had agreed the January 31 date in the first Benn Act with figures at the French Embassy in London.

Other members of the pro-Remain group – which includes former Chancellor Philip Hammond and ex-Attorney General Dominic Grieve – are suspected by Downing Street of having been assisted in drafting work by members of the European Commission.

Last night, a senior No 10 source said: 'The Government is working on extensive investigations into Dominic Grieve, Oliver Letwin and Hilary Benn [who tabled the Bill] and their involvement with foreign powers and the funding of their activities. Governments have proper rules for drafting legislation, but nobody knows what organisations are pulling these strings.

'We will demand the disclosure of all details of their personal communications with other states. The drafting of primary legislation in collusion with foreign powers must be fully investigated.'

Other members of the pro-Remain group – which includes former Chancellor Philip Hammond and ex-Attorney General Dominic Grieve (pictured) – are suspected by Downing Street of having been assisted in drafting work by members of the European Commission

However No 10 declined to discuss what evidence they had against the MPs or the exact scope of the probe.

A spokesman for Mr Hammond last night said it was 'categorically untrue' that he had drafted any legislation with the help of the EU. And Mr Grieve dismissed the allegations as 'ridiculous', adding: 'The tone of these statements comes across like the propaganda of a totalitarian state.'

The incendiary developments came as:

Foreign Secretary Dominic Raab vowed in an interview with this newspaper to thwart the 'shoddy' and 'ramshackle' Surrender Bill;

Boris Johnson arrived at the Conservative Party conference in Manchester with girlfriend Carrie Symonds while his political opponents back in Westminster ramped up their plotting, with the Scottish Nationalists leading calls for a no confidence vote;

Police investigated complaints about Brexit Party leader Nigel Farage stating 'we'll take the knife' to civil servants after Brexit, but concluded that he had not committed an offence;

No 10 strategists wargamed whether Mr Johnson could stay in power if he was forced by the courts to delay Brexit – but Tory MPs warned that he would be toppled if he did;

Jacob Rees-Mogg used an article in today's Mail on Sunday to rally the Tory troops, promising that a 'golden era awaits' after Brexit – if the party stops 'bungling Bolshevik' Jeremy Corbyn from becoming Prime Minister;

Downing Street enforcer Dominic Cummings said that Mr Johnson would emulate US President Bill Clinton by flourishing in the face of scandal and political turmoil;

An exclusive MoS survey found that voters prefer a No Deal Brexit to a Corbyn Government – including pro-Brexit Labour supporters;

A pro-Corbyn activist who is tipped to win selection for a safe Labour seat was revealed to have made vile slurs about Mr Johnson's mother;

Details emerged of how Mr Johnson arranged for his friend Jennifer Arcuri to meet Prince Andrew at Buckingham Palace;

A leak from the top secret National Security Council reveals Mr Johnson is studying plans to extract British children of Islamic State fighters from Syria, despite a Cabinet rift.

Sources say that the rebels' plans for 'Surrender Act 2' – as it has been called by Mr Cummings – includes a provision to thwart one of Mr Johnson's possible Brexit strategies.

The Prime Minister could have 'sabotaged' the EU by failing to appoint a British commissioner, with the hope that Brussels would then eject the UK from the union.

But the planned new Act would give the Commons, in the form of Mr Bercow, the power to appoint a commissioner directly. Names mentioned include Ms Rudd and former Business Secretary Greg Clark, another Remainer.

One source said: 'The Speaker is not part of the plot, but would do whatever the law of the land required him to do.

He will obey the direction of Parliament. He does not anticipate what Parliament will do, but will do what Parliament wants him to do'.

Another source added that there were divisions among the Remainer MPs, with Mr Benn and Mr Grieve wanting to delay Brexit in order to buy time to legislate for a second referendum, while Mr Letwin wanted time to reach a deal.

Another source added that there were divisions among the Remainer MPs, with Hilary Benn (pictured with Yvette Cooper) and Mr Grieve wanting to delay Brexit in order to buy time to legislate for a second referendum, while Mr Letwin wanted time to reach a deal

When The Mail on Sunday approached Mr Letwin last night about contact with foreign powers he said: 'I'm very sorry, I don't want to have a conversation about any of these things' – before terminating the conversation.

In his interview with this newspaper, Mr Raab hinted that EU law could – ironically – be used to veto the Benn Act

He said: 'The Surrender Act – which requires basically us to roll over to the most punitive conditions that Brussels could inflict on us – is a shoddy bit of legislation. The way it was put together was pretty ramshackle. It didn't have the scrutiny that you have with a Government Bill.'

Mr Raab confirmed that Ministers were examining whether they could deploy EU legislation under Article 50 of the Lisbon Treaty – which enshrines Theresa May's delayed leaving date of October 31 – to over-ride the Benn Act.

He said 'EU law has direct effect, that's one of the reasons we're leaving.

'There are multiple bits of legislation that will play out.'