What is a vote of no confidence?

Labour will table a no-confidence motion in the government later on Tuesday.

Leader Sir Keir Starmer had previously threatened to bring the vote "in the national interest" to prevent "this nonsense" about PM Boris Johnson "clinging on for a few months".

It's a vote in which MPs from all parties decide whether they want the government to continue. It can trigger a general election and could see a new prime minister appointed.

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 Keir Starmer - introduces the motion, convention means the government will provide time for a debate.

The wording of the motion is: "That this House has no confidence in Her Majesty's Government."

It needs a simple majority to pass - so it only requires one more MP to vote in favour than the number voting against.

If the government wins the no-confidence motion, it will carry on as before.

At present, the government has a big majority in the House of Commons, so it would require a lot of Conservative MPs to vote against their own government for the motion to succeed.

If the government loses, there are two things that could happen.

In normal circumstances, you would expect Parliament to be dissolved and a general election to be called.

It is also possible that the Queen could invite somebody else to form a government - someone who could win a vote of confidence in the House of Commons.

That would be very unusual - it hasn't happened since January 1924, when Stanley Baldwin's Conservatives decided to assemble a new Parliament rather than resigning, after losing their majority in a general election.

His government was defeated in a vote of no confidence and King George V asked Labour's Ramsay MacDonald - leader of the second biggest party - to form a government instead.

But almost a century later, it's not clear how that would work. It is conceivable that Conservative MPs could agree on a different leader themselves, whom the Queen could then invite to form a new government.

In principle, the monarch could even refuse to dissolve Parliament for an election.

Under the Lascelles principles (devised by Sir Alan Lascelles, private secretary to King George VI in 1950), the monarch could decline to do so if:

But these scenarios would put the monarch in a very difficult position, and it is not clear how they would play out.

If the government loses a confidence vote, the situation is similar to that of an election in which no one party wins a majority.

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.

However, if an alternative government is ready to take over, convention suggests that the PM should stand down.

But there is nothing clearly stated in law that says the prime minister must do so.

Failing to step down would risk bringing the Queen into the dispute, as the monarch appoints PMs and, in theory, can dismiss one who behaves unconstitutionally.

No - the confidence vote we had last month was just among Conservative MPs, who were asked if they still wanted Boris Johnson to be their leader.

He won by 211 votes to 148. This represented a big rebellion among members of his own party, but allowed him to carry on as prime minister, until a series of ministerial resignations subsequently led to his resignation.

It's very rare for a government to lose a no-confidence motion.

Except for the period between 2011 and March 2022, when the Fixed-term Parliaments Act was in place, prime ministers have been able to call a general election whenever they want.

That meant they could avoid a potential no-confidence vote by simply calling an election.

There has 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.