Jeremy Corbyn has called on rebel Tories and opposition leaders to stop a no-deal Brexit by ousting Boris Johnson as prime minister and allowing Labour to form a caretaker government until a general election.

The Labour leader proposed that he should lead a temporary administration on a “strictly time-limited” basis with the aim of calling a general election.

His letter threw down the gauntlet to the Lib Dems, the SNP, Plaid Cymru, the Greens and rebel Tories, at a time when MPs opposed to no deal have been discussing a “national unity government” led by a centrist figure.

Corbyn’s proposal makes it clear that the Labour frontbench consider he is the only politician who could lead a caretaker government, rather than a backbench candidate such as Tory veteran Ken Clarke or Labour’s Yvette Cooper.

Jeremy Corbyn (@jeremycorbyn) I've written to the leaders of other political parties and senior backbenchers from across Parliament to lay out my plan to stop a disastrous No Deal Brexit and let the people decide the future of our country. pic.twitter.com/Jz1MjXCrqk

Jo Swinson, the leader of the Lib Dems, immediately dismissed the idea that Corbyn could be a caretaker prime minister, saying: “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.”

But others were more amenable with the SNP and Plaid Cymru responding to say they would be willing to enter talks, although Liz Saville Roberts, the Plaid leader, said it was “extremely disappointing” that Corbyn would not support a second referendum first and general election second.

Caroline Lucas, the Green MP, agreed with Plaid Cymru that the offer of talks was welcome but she argued “holding a general election before a people’s vote is the wrong way around”.

Ian Blackford, the SNP leader in Westminster, who had previously asked Corbyn to join talks, said: “I am pleased to receive his letter today confirming that Labour will now work with the SNP and others collaboratively to stop the UK government – but this means Labour needs to get off the fence on Brexit.”

The others approached for talks were Dominic Grieve, Caroline Spelman, Oliver Letwin and former Conservative Nick Boles, but not any of the Independent Group for Change UK MPs, independent or other former Labour MPs who have left the party. Grieve said he would be “considering it with colleagues” but several Conservative would-be rebels told the Guardian they could not contemplate a national unity government that made Corbyn prime minister.

In his letter, Corbyn said: “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.

“Following a successful vote of no confidence in the government, I would then, as leader of the opposition, seek the confidence of the House for a strictly time-limited temporary government with the aim of calling a general election, and securing the necessary extension of article 50 to do so.”

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The Labour leader said he was offering talks with MPs across the parties in order to build support for a vote of no confidence in the government, although he did not say when this would be brought. The Labour leadership’s argument is that if MPs are serious about stopping a no-deal Brexit then they will have to get behind his plan.

The opposition could attempt an immediate vote in the first week of September in the hope an election could be fitted in before Brexit deadline day of October 31, but it is not clear there is yet enough support from Conservative backbenchers for this to be successful.

Corbyn’s letter came on a dramatic day in parliamentary recess, as Johnson ramped up his rhetoric against MPs who are working to block a no-deal Brexit.

The prime minister was accused of echoing the rhetoric of the second world war as he said some MPs were in “terrible collaboration” with the EU to prevent the UK leaving on 31 October.

His comments were an apparent swipe at Philip Hammond, the former chancellor, who on Tuesday wrote with 19 colleagues to the prime minister accusing him of setting the bar too high for a deal with the EU and warning that crashing out without a deal would be a betrayal of the referendum result

One Conservative MP, Guto Bebb, said Johnson’s language was “despicable” and “absolutely disgraceful” in light of threats made to some MPs over the issue of Brexit and the murder of Labour’s Jo Cox.

However, Downing Street sources said Johnson had simply been trying to make the point that the EU is “looking at what is happening here and getting the entirely wrong message that parliament is somehow going to block Brexit on 31 October”, which he claims will make Brussels less likely to offer concessions.

On a Facebook live stream, while answering pre-selected questions from the public, Johnson conceded that the chances are a no-deal Brexit are now becoming more likely, while dismissing the idea that MPs will be able to stop him.

In a sign that Whitehall preparations are stepping up, the Department of Health and Social Care announced a £25m contract to set up an “express freight service” to deliver medicines and medical products into the country in the event of a no-deal Brexit, potentially lasting for up to two years.

MPs are deeply divided over how and whether it is possible to stop no deal on 31 October but most Conservatives battling that outcome would rather start with legislative options to prevent the UK from crashing out. The primary method would be to amend legislation to mandate the prime minister to seek an extension.

What the Tories refer to as the “nuclear option” is a vote of confidence in the prime minister, which could bring down the government and give rebels a 14 day period to form a new administration to ask for an extension from the EU. They are also looking at the possibility of trying to use this period to force Johnson as prime minister to seek an extension from the EU, without ousting him from No 10.

If no MP can win a confidence vote in the fortnight after the first vote, then a general election is triggered. Johnson refused on Wednesday to rule out the idea that he could simply schedule an election for after 31 October, when the UK is due to leave with or without a deal.

“I think the British public have had a lot of elections and electoral events,” he said when asked if would call one for the days after Brexit. “There was the election in 2015, the referendum in 2016, another election in 2017. I think what they want us to do is get on and deliver Brexit on 31 October. I never tire of telling you that’s what we’re going to do.”

Corbyn wrote to Mark Sedwill, the cabinet secretary, last week demanding that he intervene to make clear the prime minister would not be allowed to do that under purdah rules, which restrict policy-making during election periods. Sedwill replied on Wednesday declining to clarify the purdah rules, saying they would be applied according to the circumstances.

A No 10 spokesman responded to Corbyn’s letter saying there was a “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 that the people are the servants and politicians can cancel public votes they don’t like,” he added.