The Tory party has “failed” the UK and a general election is the “change of direction the country needs”, Jeremy Corbyn is set to say in a speech later.
The Labour leader will say the UK is facing a Brexit “crisis” and will vow to do “everything necessary” to stop the UK leaving the EU without a deal.
It comes after a leaked government report warned of food and medicine shortages in a no-deal exit.
Cabinet minister Michael Gove said it outlined a “worst-case scenario”.
Mr Corbyn will give the speech as part of his trip to Northamptonshire.
And shadow chancellor John McDonnell told the BBC that Mr Corbyn will meet other British political leaders next week to discuss tactics to prevent a no-deal Brexit.
He also supported calls for the House of Commons to be recalled “in the next few days” to allow MPs to debate the prospect of a no deal. Parliament could be reconvened if the government put a request in to the Speaker John Bercow.
Mr Gove, who is responsible for no-deal preparation, said the leaked cross-government study, codenamed Operation Yellowhammer, was old and that Brexit planning had accelerated since Boris Johnson became prime minister.
A No 10 source told the BBC it was leaked to the Sunday Times by a disgruntled ex-minister in an attempt to influence discussions with EU leaders.
But Lord Kerslake, a former head of the civil service, said the dossier “lays bare the scale of the risks we are facing”.
How could a general election be called?
Prime Minister Boris Johnson – whose government has a working majority in Parliament of one – has ruled out holding a general election before the 31 October Brexit deadline.
But Mr Corbyn plans to win a vote of no-confidence in the government, which would begin a crucial 14-day period, after which a general election could automatically be triggered.
To stop that automatic election taking place, the existing government, or an alternative one formed during that period, must persuade MPs to pass a vote of confidence.
Within the two weeks, Mr Corbyn wants to become a temporary PM, then delay Brexit and call a snap election.
There are no firm rules about who, if anyone, should get the chance to form an alternative government during the 14-day period.
Liberal Democrat leader Jo Swinson called Mr Corbyn “divisive” before suggesting Tory MP Ken Clarke or former Labour leader Harriet Harman would do a better job.
However, Mr McDonnell said it was “not negotiable” that Mr Corbyn would lead a temporary government if Mr Johnson was defeated in a vote of no confidence.
If Mr Johnson survives a vote of no-confidence, a general election appears unlikely before the UK leaves the EU.
What will Mr Corbyn say in his speech?
Mr Corbyn will say the Tories have “lurched to the hard right under Boris Johnson”, calling him “Britain’s Trump”.
“A general election triggered by the Tory Brexit crisis will be a crossroads for our country. It will be a once-in-a-generation chance for a real change of direction, potentially on the scale of 1945 or 1979,” he will say.
“Labour believes the decision on how to resolve the Brexit crisis must go back to the people.”
What is the Conservatives’ response?
Conservative Party chairman James Cleverly said Mr Corbyn offers more “dither and delay”.
“This is a cynical attempt to seize power by a man who would wreck the economy, is soft on crime and won’t stand up for Britain,” he said.
“Only Boris Johnson and the Conservatives can provide the leadership Britain needs and deliver Brexit by 31 October, whatever happens.”
Mr Johnson is travelling to France and Germany to meet EU leaders later this week.
The prime minister will insist there must be a new Brexit deal when he holds talks with German Chancellor Angela Merkel and French President Emmanuel Macron.
What did the leaked no-deal document say?
The leaked dossier said leaving the EU without a deal could lead to:
- Fresh food becoming less available and prices rising
- A hard Irish border after plans to avoid checks fail, sparking protests
- Fuel becoming less available and 2,000 jobs being lost if the government sets petrol import tariffs to 0%, potentially causing two oil refineries to close
- UK patients having to wait longer for medicines, including insulin and flu vaccines
- A rise in public disorder and community tensions resulting from a shortage of food and drugs
- Passengers being delayed at EU airports, Eurotunnel and Dover
- Freight disruption at ports lasting up to three months, caused by customs checks, before traffic flow improves to 50-70% of the current rate.