The prime minister narrowly survived a vote of confidence among Tory MPs last month - but suffered a rebellion bigger than Theresa May.

Some 211 MPs voted for the prime minister, compared to 148 votes against - a majority of 63.

He needed a simple majority - 180 votes or more - to continue in office.

However the result meant 59% of Conservative MPs backed Mr Johnson, with 41% voting against him.

Javid delivers damning speech after quitting - Politics Hub

Under current rules, the prime minister is now immune from another leadership challenge for 12 months.

But now, less than a month on from surviving the leadership challenge, the PM's leadership looks in peril as a flurry of ministers quit the government in protest at Downing Street's handling of a series of recent scandals.

The latest of these being Mr Johnson promoting Chris Pincher to the role of deputy chief whip in February despite being told of a sexual misconduct complaint against the Tamworth MP in 2019.

On Tuesday, the PM apologised for allowing this job move to take place - but this did not stop the resignations of both his health secretary Sajid Javid and chancellor Rishi Sunak minutes later.

As of early Wednesday afternoon, more than 30 Conservative MPs have now resigned from their government roles.

But what could happen now and how would a potential leadership challenge work?

Boris Johnson resigns

Despite insisting at PMQs that he will not leave Number 10 even though he is facing a mounting revolt against his leadership, Mr Johnson could still decide to resign if more of his ministerial team quit.

If this was to happen, a leadership contest will be held to decide his replacement.

The 1922 Committee would set the timetable for the contest.

To take part in the race, a Tory MP has to be nominated by eight colleagues.

If more than two MPs put themselves forward and secure enough nominations to run for leader, a series of secret ballots will be held to whittle them down.

The individual who receives the fewest number of votes will be eliminated after every round until two candidates remain.

When just two MPs are left in the race, party members get to make their final choice before a deadline set by the 1922 Committee.

The winner will become Conservative Party leader and PM.

Assuming the new leader was able to command the confidence of the House of Commons, they would not be required to call a general election.

However, a new leader could choose to call an election if they wanted to secure their own mandate.

Because the process could take several weeks and the Conservative Party still have a majority government, the cabinet could nominate an interim PM before the party holds a proper leadership contest to choose a permanent successor to Mr Johnson.

Current Deputy PM Dominic Raab or new chancellor Nadhim Zahawi could be among those in the frame.

Mr Johnson could also stay in post until a new leader of the Conservative Party is elected.

Another confidence vote

As mentioned before, under the current rules the PM cannot face another confidence vote for 12 months if they survive one.

This means Mr Johnson is effectively immune from being ousted by his own MPs until June 2023.

However, the 1922 Committee Executive - the heads of the group of Conservative backbench MPs - met in private at 4pm to discuss a potential rule change which could see a prime minister able to face more than one leadership challenge a year.

They decided that elections to the committee's ruling executive, for which there are 18 places, will take place on Monday.

Discussions on whether the rule change should take place will then begin.

It could therefore mean that Mr Johnson's fate may ultimately lie with backbench MPs if the Tory 1922 Committee's rules are altered to allow another confidence vote in the near future.

If it were to be decided that confidence votes should be able to occur more frequently, then the process to trigger another one can begin again.

How do confidence votes work?

This involves MPs disgruntled with their party's current leadership can submitting no confidence letters to the committee's chairman, registering their disapproval.

The Conservative Party rules state that at least 15% of Tory MPs must write a no confidence letter to make a leadership challenge possible.

This currently equates to 54 Tory MPs needing to submit letters to chairman Sir Graham Brady - a target which, given the number of public announcements calling for the PM to resign in recent days, would be likely to be met in the near future.

Letters are handed in confidentially, so no accurate total of how many have been submitted to Sir Graham is publicly available. He is therefore likely the only person who knows the real tally.

Those who submitted letters of no confidence prior to the vote in June would have to submit them again for them to be counted once more.

Once the threshold is reached, a vote will take place in the form of a secret ballot where all Conservative MPs will have to decide if they back the current leader or not.

Mr Johnson would have to secure the backing of half of his MPs plus one to survive - currently 180.

If he were to lose, there would be a leadership contest and he would be barred from entering.