AS Theresa May enters a “critical” week for her Brexit deal amid criticism on several fronts, speculation that she may face a vote of no confidence from dissatisfied Conservative MPs has ratcheted up.

Here is how a Tory leadership contest could unfold:

How would it begin?

To trigger a vote of no confidence, 15 per cent of Tory MPs – 48 in total – must write to the chairman of the Conservative backbench 1922 Committee, Sir Graham Brady.

How many have sent letters so far?

It is impossible to say for certain, as Sir Graham keeps the actual number a closely guarded secret. According to reports around 25 have publicly submitted letters, although more could have sent them anonymously.

On Sunday the Prime Minister said she was aware that the number had not reached 48, while Sir Graham also confirmed it had not been hit.

Members of the pro-Brexit European Research Group believe the figure is close. Crispin Blunt told The Guardian he expects it will be reached, telling The Guardian it is “in the Prime Minister’s interests that it’s got out of the way”.

Who has sent letters so far?

Steve Baker (Wycombe), Nadine Dorries (Mid-Bedfordshire), Sheryll Murray (South-East Cornwall), Henry Smith (Crawley), Lee Rowley (North-East Derbyshire), Simon Clarke (Middlesbrough South and East Cleveland), Jacob Rees-Mogg (Somerset North-East), Martin Vickers (Cleethorpes), Laurence Robertson (Tewkesbury), Andrea Jenkyns (Morley & Outwood) Peter Bone (Wellingborough & Rushden), James Duddridge (Rochford and Southend East), Anne Marie Morris (Newton Abbott), Philip Davies (Shipley), Andrew Bridgen (North-West Leicestershire), Adam Holloway (Gravesham), John Whittingdale (Maldon), Mark Francois (Rayleigh and Wickford), Maria Caulfield (Lewes), Ben Bradley (Mansfield and Warsop), Chris Green (Bolton West & Atherton), Zac Goldsmith (Richmond Park and North Kingston), Sir William Cash (Stone).

Two Conservative MPs who are widely reported to have submitted letters told the Press Association that they are not confirming publicly whether they have in fact done so.

Marcus Fysh told PA the question of whether letters have been submitted is “a private thing between Graham Brady and an MP”.

But he added: “I have been disillusioned for a long time and I think we do need a leader who can reset the policy and if she isn’t willing to, we need someone else.”

David Jones said: “I have not made public whether or not I have submitted a no confidence letter.”

What if they do reach the 15 per cent threshold?

A vote would be held among Tory MPs. Mrs May would need the support of more than 50 per cent of the 315 Conservative MPs to stay in office. But even if she wins, if the margin of victory is small her authority may have been fatally wounded.

What if she loses?

If the PM lost the vote, she would not be able to stand in the subsequent leadership contest arranged by Sir Graham.

How would that work?

Candidates for the leadership must be nominated by two Conservative MPs. If only one candidate comes forward, he or she becomes leader. If a number of would-be leaders are nominated, the list is whittled down to a shortlist of two in a series of votes by MPs.

The final pair then go to a postal ballot of all party members, with the position of leader going to the victor.

How long would that take?

Sir Graham would be responsible for overseeing the contest and setting a timetable for the campaign, which would be expected to last around 12 weeks – although those calling for Mrs May to go believe it could be accomplished much quicker.

Mrs May could remain in the post during the campaign period.

The 1922 Committee seems to have a key role, what exactly is it?

Widely known in Westminster as “the ‘22”, the committee of all backbench Conservative MPs meets weekly when the House of Commons is sitting.

Where does the unusual name come from?

The committee takes its name from a meeting of Conservative MPs on October 19, 1922. The MPs successfully ended the party’s coalition with the Liberals, bringing down the government of David Lloyd George. The resulting general election was won by the Tories.