Jeremy Corbyn is leaving open the option of supporting an alternative caretaker prime minister, as he vows to do “everything necessary to stop a disastrous no-deal Brexit”.

In a speech in the midlands, the Labour leader will not rule out backing a different stopgap, after the Liberal Democrats and rebel Tories dismissed putting him in No 10 to avert a crash-out on 31 October.

Aides said he remained focused on seeking to persuade MPs to back him, if Boris Johnson can be toppled in a no-confidence vote – but described it only as the “simplest and most democratic” solution.

Over the weekend, Mr Corbyn’s prospects faded when two senior Conservative rebels, Dominic Grieve and Oliver Letwin, said he was not an acceptable leader of an “emergency government”.

“We will do everything necessary to stop a disastrous no deal, for which this government has no mandate,” Mr Corbyn will tell an audience in the marginal Tory seat of Corby.

Tariffs in the event of a no-deal Brexit Show all 15 1 /15 Tariffs in the event of a no-deal Brexit Tariffs in the event of a no-deal Brexit Pork There will be tariffs on pork in order to protect British farmers Getty Tariffs in the event of a no-deal Brexit Cheese There will be tariffs in place on some cheeses including €22.10/100kg of cheddar, €19.10/100kg of processed cheese and €18.60/100kg on some blue cheeses Getty Tariffs in the event of a no-deal Brexit Milk There will be no tariffs in place on milk Getty Tariffs in the event of a no-deal Brexit Car Parts There will be no tariffs on car parts imported from Europe PA Tariffs in the event of a no-deal Brexit Cars However finished cars will face tariffs of 10.6% Getty Tariffs in the event of a no-deal Brexit Alcoholic drinks There will be no tariffs on alcoholic drinks - except on some rums due to ingredients used in their distilling process Getty Tariffs in the event of a no-deal Brexit Beef There will be tariffs on beef in order to protect British farmers Getty Tariffs in the event of a no-deal Brexit Fish There will be no tariffs on many types of fish including cod, haddock, salmon and sea bass Getty Tariffs in the event of a no-deal Brexit Fruit and vegetables There will be no tariffs on almost all fruit and vegetables Getty Tariffs in the event of a no-deal Brexit Chocolate There will be no tariffs on chocolate or other cocoa products Getty Tariffs in the event of a no-deal Brexit Poultry There will be tariffs on poultry in order to protect British farmers Getty Tariffs in the event of a no-deal Brexit Ceramics There will be some tariffs in place on ceramis Getty Tariffs in the event of a no-deal Brexit Steel There will be no tariffs on steel Getty Tariffs in the event of a no-deal Brexit Coal There will be no tariffs on coal Getty Tariffs in the event of a no-deal Brexit Lamb/Mutton There will be tariffs on the meat of sheep in order to protect British farmers Getty

The choice of words suggests both an alternative caretaker or legislation to bind Mr Johnson’s hands would be acceptable to the Labour leader if he failed to get the numbers.

Mr Corbyn will add: “The Conservative Party’s failure on Brexit, and its lurch to the hard right, has provoked the crisis our country faces this autumn.

“After failing to negotiate a Brexit deal that would protect jobs and living standards, Boris Johnson’s Tories are driving the country towards a no-deal cliff edge.”

Last week, the Labour leader pledged to call an immediate general election, to ease the fears of opposition MPs, and to deliver a Final Say referendum on Brexit if he wins.

But Jo Swinson, the Liberal Democrat leader, described the plan as “nonsense”, because Mr Corbyn was incapable of uniting MPs, although she later agreed to talks.

And Mr Grieve, the leading Tory plotter, dealt him a blow by saying: “I am not about to facilitate Jeremy Corbyn’s arrival in Downing Street.” – a verdict echoed by Sir Oliver.

Vince Cable said the Lib Dems wanted a guarantee from Mr Corbyn that, if he could not win backing in the Commons to be the caretaker prime minister, he would support another candidate.

Speaking in Corby, Mr Corbyn will say: “Labour believes the decision on how to resolve the Brexit crisis must go back to the people.

“And if there is a general election this autumn, Labour would commit to holding a public vote, to give voters the final say, with credible options for both sides, including the option to remain.”

Mr Corbyn will also argue that, while a no-deal Brexit is a huge threat to the country, the UK faces even greater problems, putting Britain at “a crossroads”.