There is growing speculation that MPs will table a vote of no confidence in the government, to try to stop a no-deal Brexit on 31 October.
There is speculation that MPs could call for a vote of no confidence in the government, to try to stop a no-deal Brexit on 31 October.
The opportunities for holding such a vote have been reduced by Boris Johnson's request for Parliament to be suspended from 10 September.
But what is it and what happens if the government loses?
What is a no confidence vote?
What is a no confidence vote?
It is a chance for MPs to hold a vote on whether they want the government to continue - and it has the power to trigger a general election.
It's a vote in which MPs from all parties decide whether they want the government to continue. It has the power to trigger a general election and could see a new prime minister appointed.
Any MP can propose a motion of no confidence, but that doesn't mean it would be debated.
While any MP can propose a no confidence motion, there's no guarantee their request will be granted.
However, if the leader of the opposition - currently Labour leader Jeremy Corbyn - introduces the motion, convention means the government will provide time for a debate to take place.
However, if the leader of the opposition - currently Labour leader Jeremy Corbyn - introduces the motion, convention means the government will provide time for a debate.
The wording of a no-confidence motion is: "That this House has no confidence in Her Majesty's Government."
The wording of a no-confidence motion is: "That this House has no confidence in Her Majesty's Government."
The motion needs a simple majority to pass - so it only requires one more MP to vote in favour than the number voting against.
It needs a simple majority to pass - so it only requires one more MP to vote in favour than the number voting against.
Is there enough time?
If the government wins the no confidence motion, it carries on as before. At present, the government cannot count on winning as it has a minority of seats in the House of Commons.
The earliest the vote could take place is 4 September.
What happens if the government loses?
If the government wins, it carries on as before.
If the government loses, it has 14 days to try to win back the confidence of MPs through another vote. At the same time, opposition parties can try to form their own alternative government.
But, if the government loses, MPs would have only three or four sitting days to form an alternative government before Parliament is closed. During this time the new government would have to show it has majority support in the House of Commons.
If nothing is resolved at the end of the 14-day period, the rules say a general election is automatically triggered.
After a lost no-confidence vote there would usually be a 14-day period before a general election can be triggered.
At this point, the prime minister advises the Queen on the date the general election will take place.
What would happen if the government loses?
Parliament will then dissolve 25 working days before polling day. When this happens, Parliament no longer sits and MPs stop being MPs while they campaign for re-election.
To prevent an automatic general election taking place, the existing government - or an alternative one formed during that period - must persuade MPs to pass a vote of confidence.
Would the PM have to resign?
The wording of the confidence motion has to be: "That this House has confidence in Her Majesty's Government."
If the government loses a confidence vote, the situation is similar to that of an election in which no one party wins a majority.
At the end of the standard 14 day period, assuming such a motion hasn't passed, the prime minister advises the Queen when the general election will take place.
That means that the existing prime minister should only resign if it's clear someone else can command the support of the House of Commons.
Parliament is dissolved 25 working days before the general election date.
However, if an alternative government is ready to take over, convention suggests that the PM should stand down.
It is unclear what would happen if the PM lost a no confidence vote and Parliament was suspended before the 14-day period was up. However there would certainly be political pressure on the government to postpone prorogation.
Yet there is nothing clearly stated in law that says the prime minister must do so.
There are no firm rules about who, if anyone, should get the chance to form an alternative government during the 14-day period.
Failing to step down would risk bringing the Queen into the Brexit dispute, as the monarch appoints PMs and, in theory, can dismiss one who behaves unconstitutionally.
The Cabinet Manual - a document which sets out the main rules covering the working of government - suggests that the principles applied should be similar to those after an election in which no one party wins a majority.
Where do the parties stand on a no confidence vote?
That means that the old prime minister should only resign if and when it's clear that somebody is more likely to have the support of MPs.
Jeremy Corbyn says Labour wants to introduce a no confidence motion.
So it's possible that the existing prime minister would stay in place, or that more than one leader would get a chance.
But he says it will only do this once the threat of a no-deal Brexit on 31 October has been removed.
Labour leader Jeremy Corbyn has urged MPs from all parties to install him as prime minister, following a no confidence vote.
However, the government accuses Labour of running scared. It says Labour should immediately bring a vote of confidence to end the Brexit stalemate.
But the new prime minister does not have to be the leader of the opposition.
If a no confidence vote were to pass, Jeremy Corbyn has urged MPs from all parties to install him as prime minister. Mr Corbyn says he would then immediately extend the Brexit deadline and ask Parliament to call an early election.
Liberal Democrat leader Jo Swinson has suggested that former Conservative chancellor Ken Clarke or former Labour deputy leader Harriet Harman - the longest-continuously serving male and female MPs - could head a temporary government.
SNP leader Nicola Sturgeon has hinted she might back Jeremy Corbyn becoming a "caretaker" prime minister.
Could the prime minister refuse to resign?
However, Liberal Democrat leader Jo Swinson says many MPs will not unite behind Jeremy Corbyn. Ms Swinson suggests that former Conservative chancellor Ken Clarke or former Labour deputy leader Harriet Harman should head a temporary government instead.
If an alternative government is ready to take over, the existing prime minister would be expected to resign. However, there is nothing clearly stated in law that says the prime minister must do so.
But failure to resign in such circumstances would risk bringing the Queen into the heart of the Brexit dispute. Ultimately, it is the Queen that appoints prime ministers and in theory the monarch can dismiss a prime minister who behaves unconstitutionally.
But such a situation is very unlikely, according to Maddy Thimont-Jack, at the Institute for Government think tank.
"If there is clearly someone else who could form a majority or has majority support in Parliament, the political pressure would be such that the prime minister would be obliged to resign. It's an extremely important and established political convention," she says.
How could the prime minister be defeated?
Boris Johnson has a wafer-thin majority in Parliament. The loss of the Brecon by-election to the Lib Dems has reduced it to one.
Since the 2017 general election the Tories have been reliant on the 10 DUP MPs in the House of Commons. And their majority has become narrower over time after a series of defections.
So, if some Tories are prepared to vote against them in a no-confidence vote the new prime minister could be in office for only a brief period.
Previous no confidence votes
Previous no confidence votes
Before the law was changed in 2011 to say elections would be held every five years, the rules governing votes of no confidence were different.
It's very rare for a government to lose a no confidence motion.
Prime ministers had the power to call general elections whenever they wanted. That meant they could turn votes on particular bits of legislation into "confidence votes".
Before 2011, prime ministers could call a general election whenever they wanted to. That meant they could evade a possible no confidence vote by calling an election instead.
In other words they would threaten to call an election unless MPs backed a new law.
However, this is no longer an option. Elections are only triggered by no-confidence votes with precisely the right wording.
However, the fundamental principle remains the same. Governments can only continue if they have the confidence of the House of Commons.
There's only been one occasion since World War Two when the government lost a no-confidence vote.
There's only been one occasion since World War Two when the government lost a no-confidence vote.
That was in 1979, when the Labour minority government fell and was replaced by Margaret Thatcher's Conservatives at the general election which followed.
That was in 1979, when the Labour minority government fell and was replaced by Margaret Thatcher's Conservatives at the general election which followed.
