JEREMY Corbyn is stepping up moves to form a united front with fellow opposition leaders and senior Remainer Conservatives to stop Boris Johnson leading Britain into a “deeply damaging” no-deal Brexit.

In a significant development, the Labour leader gives his clearest signal yet that he hopes to build enough cross-party support to table a no-confidence vote to bring down the Conservative Government as early as next month when MPs return from their summer break.

Mr Corbyn’s plan would then involve him leading a "strictly time-limited" caretaker government, securing a further extension to Article 50, and holding a general election.

A Labour victory would lead to a new negotiated deal with Brussels and another referendum on it.

But the Liberal Democrats gave Mr Corbyn’s plan short shrift, branding it “nonsense”.

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The Labour leader’s move comes after the Prime Minister accused Remainer MPs and the EU of being engaged in a “terrible kind of collaboration” to block Brexit.

In his first People’sPMQs broadcast from his desk in Downing St, Mr Johnson said: “Our European friends are not…compromising at all on the Withdrawal Agreement even though it's been thrown out three times; they're sticking to every letter, every comma of it - including the backstop - because they still think Brexit can be blocked in Parliament.”

His remarks were a riposte to an earlier intervention from Philip Hammond, who said a no-deal outcome would be a “betrayal” of the 2016 referendum result, that could cause "irreparable damage" to the Union of the United Kingdom.

The former Chancellor suggested the PM was not in charge of the Government’s Brexit strategy and it was the likes of his key adviser Dominic Cummings, the former Leave campaign chief, who were “pulling the strings” in Downing St to realise a no-deal outcome.

Nonetheless, Mr Hammond insisted he was “very confident” Parliament had the means to “make its voice heard and to pass legislation” to prevent a no-deal outcome.

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What Mr Corbyn described as a “non-committal reply” he received from Sir Mark Sedwill, the Cabinet Secretary and head of the civil service, on Tuesday appears to have galvanised the Labour leader into action.

With suggestions that the Prime Minister could call a snap poll directly after Britain left the EU on October 31 - deal or no-deal - Mr Corbyn last week called on Sir Mark to rule that Mr Johnson could not force through a no-deal Brexit in the middle of a general election campaign.

Such a move, he believes, would be an “anti-democratic abuse of power” as it would deprive voters of a choice on Britain’s EU future in such an election campaign.

Mr Corbyn’s letter has been sent to Ian Blackford, Jo Swinson, Liz Saville Roberts and Caroline Lucas, the respective leaders of the SNP, Liberal Democrats, Plaid Cymru and the Greens at Westminster, as well as senior Tories opposed to a no-deal Brexit; Dominic Grieve, Oliver Letwin, Nick Boles and Caroline Spelman.

In it, the Labour leader seeks to build support for a vote of no-confidence in the Government, writing that “our priority should be to work together in Parliament to prevent a deeply damaging no-deal”.

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Mr Corbyn makes clear that if the vote of no-confidence were successful, he would seek to form a temporary caretaker government with the aim of calling a general election and securing the necessary extension of Article 50 to hold it.

He writes: “While it is likely that the issue will be contested in the courts, our priority should be to work together in Parliament to prevent a deeply damaging no-deal being imposed on the country, denying voters the final say.

“This government has no mandate for no-deal and the 2016 EU referendum provided no mandate for no-deal. I, therefore, intend to table a vote of no-confidence at the earliest opportunity when we can be confident of success.”

The Labour leader suggests a meeting with fellow party leaders and senior Tories to discuss his strategy further, which he stresses “can halt the serious threat of no-deal, end the uncertainty and disarray, and allow the public to decide the best way ahead for our country”.

He ends the letter by reiterating how in a general election, Labour would be committed to a public vote on the terms of Brexit, including an option to Remain; although he does not say whether his party would campaign for a Labour deal or for Britain to stay in the Brussels bloc.

Mr Blackford welcomed Mr Corbyn’s offer of deeper collaboration but stressed that urgent action to find “cast-iron solutions” was needed to “prevent the greatest act of self-harm to our economy”.

However, Ms Swinson was hostile to the Labour leader’s move.

She said: “Jeremy Corbyn is not the person who is going to be able to build an even temporary majority in the House of Commons for this task; I would expect there are people in his own party and indeed the necessary Conservative backbenchers who would be unwilling to support him. It is a nonsense.”

The Lib Dem leader insisted she was committed to working with others in a “credible way” but added: "This letter is just more red lines that are about him and his position and is not a serious attempt to find the right solution and build a consensus to stop a no-deal Brexit.”

No 10 responded with a spokesman saying: “There is a clear choice: either Jeremy Corbyn as Prime Minister who will overrule the referendum and wreck the economy or Boris Johnson as Prime Minister who will respect the referendum and deliver more money for the NHS and more police on our streets.

“This Government believes the people are the masters and votes should be respected; Jeremy Corbyn believes the people are the servants and politicians can cancel public votes they don’t like.”

As ministers and MPs prepare themselves for a September Brexit showdown in the Commons, it has been suggested Mr Cummings believes any move by opposition leaders is too late.

The argument goes that even if the PM were to lose a no-confidence vote, the law enables him to recommend to the Queen an election after October 31; so, Brexit, deal or no-deal, would be a fait accompli.