Boris Johnson is likely to face an immediate challenge to his government if he tries to force through a no-deal Brexit after becoming prime minister.
Having won the Tory leadership race and got into Number 10, Mr Johnson could be ousted not long after taking the job if MPs decide to back a vote of no confidence in his government.
During his campaign to be Tory leader, Mr Johnson insisted Britain must leave the European Union by the end of October, come what may.
But a number of Conservative MPs are unhappy with that strategy, and are prepared to vote against Mr Johnson if a no-confidence vote is held in Parliament.
A no confidence vote is an opportunity for MPs to decide if the government should continue - Theresa May’s administration survived one at the beginning of this year.
While any MP can propose a motion of no confidence, convention dictates it will only be debated if introduced by the leader of the opposition.
All eyes will be on Labour leader Jeremy Corbyn in the wake of the Tory leadership contest, although it is likely he will wait until after Parliament’s summer recess.
The wording of the motion reads: “That this House has no confidence in Her Majesty's Government.”
Should Mr Johnson’s government lose such a vote, it or an alternative government would be given 14 days to win a vote of confidence.
If it is successful, that government can continue its business, but if MPs cannot agree on an alternative prime minister, a general election is triggered seven weeks after the no confidence vote.
Since the 2017 general election, the Conservative government has depended on the support of 10 DUP MPs in the House of Commons, so if there are enough Tory rebels, Mr Johnson could be out of Number 10 almost immediately.
A number of senior Tories have indicated they will vote against the government if it presses ahead with a no-deal Brexit.
The former attorney general Dominic Grieve said a number of Conservatives will feel they have no choice but to vote down Mr Johnson’s government.
“Blocking no deal technically may be quite difficult but as I’ve said on many occasions in the last 12 months, if the government persists in trying to carry out a no-deal Brexit I think that administration is going to fall,” he said.
“My impression talking to colleagues in the house is if we get to the point where no deal becomes a real prospect then there are going to be more colleagues opposed to it because they think it is going to be catastrophic,” he said.
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Senior Tory Kenneth Clarke has also indicated he would consider voting against the government, while others are keeping their cards close to their chests.
However, defence minister Tobias Ellwood has said “a dozen or so” Tory MPs would support a vote of no confidence to prevent a no-deal Brexit, meaning it could have the required numbers to pass.
However, it has been reported that up to 10 Labour MPs are prepared to back a no-deal Brexit rather than remain in the EU.
Sir Roger Gale, the Conservative MP for North Thanet, has predicted that enough Tory MPs would support the vote of no confidence if Mr Corbyn holds off lodging it until after the summer recess.
Sir Roger said: “What may happen is if enough Tories can persuade the leader of the opposition or his troops to hold fire on a vote of no confidence until, say, the beginning of October, by which time if it were to be Mr Johnson he would have had the chance to prove whether he’s messing around or whether he can actually do anything, and then there was a vote of no confidence, I think Johnson would lose it.”
Last Thursday, MPs backed a bid to stop Mr Johnson suspending Parliament in order to force through a no-deal Brexit should be become prime minister.
Mr Johnson has refused to rule out proroguing Parliament to prevent MPs from blocking a no-deal scenario.
A majority of 41 MPs approved an amendment blocking prorogation between October 9 and December 18.
Four cabinet ministers, including chancellor Philip Hammond, abstained from the vote.
Mr Hammond said at the weekend he would resign if Mr Johnson became prime minister.
Asked if he would back a motion of no-confidence in the new government, Mr Hammond said he could “not exclude anything”.
“You cannot and should not bypass Parliament in this fashion,” said Sir John. “I cannot imagine how anyone could conceivably think that is right.”