A beleaguered Theresa May will face Conservative MPs demanding she quit just hours before the Commons stages historic votes to snatch control of the Brexit process.

The twin threats will rear up on Wednesday, after MPs openly joked Ms May’s shattered authority meant Oliver Letwin – the senior Tory behind the move to hold “indicative votes” – is the “new prime minister”.

At a meeting of the 1922 committee of backbench Tory MPs, the prime minister will come under huge pressure to set out a timetable for her departure from Downing Street, as a last-gasp bid to rescue her deal.

A visit to No 10 by Graham Brady, the 1922’s chair and backbenchers’ steward, sparked fresh speculation that he was delivering a message that her time was up.

A senior Democratic Unionist Party MP suggested his party now preferred a long Brexit delay to approving her deal, making it even less likely a third “meaningful vote” can be won – or will even be held this week.

Meanwhile, up to 20 junior ministers are thought to be ready to resign if the prime minister refuses to grant free votes on all the Brexit options on Wednesday evening.

More clues emerged as to how the indicative votes process will unfold. The votes are the first step to potential legislation to force the government to adopt parliament’s solution to the deepening crisis.

Put It To The People march: Best of The Independent’s pictures Show all 24 1 /24 Put It To The People march: Best of The Independent’s pictures Put It To The People march: Best of The Independent’s pictures Put It To The People protest 23 March 2019 Angela Christofilou/The Independent Angela Christofilou/The Independent Put It To The People march: Best of The Independent’s pictures Put It To The People protest 23 March 2019 Angela Christofilou/The Independent Angela Christofilou/The Independent Put It To The People march: Best of The Independent’s pictures Put It To The People protest 23 March 2019 Angela Christofilou/The Independent Angela Christofilou/The Independent Put It To The People march: Best of The Independent’s pictures Put It To The People protest 23 March 2019 Angela Christofilou/The Independent Angela Christofilou/The Independent Put It To The People march: Best of The Independent’s pictures Put It To The People protest 23 March 2019 Angela Christofilou/The Independent Angela Christofilou/The Independent Put It To The People march: Best of The Independent’s pictures Put It To The People protest 23 March 2019 Angela Christofilou/The Independent Angela Christofilou/The Independent Put It To The People march: Best of The Independent’s pictures Put It To The People protest 23 March 2019 Angela Christofilou/The Independent Angela Christofilou/The Independent Put It To The People march: Best of The Independent’s pictures Put It To The People protest 23 March 2019 Angela Christofilou/The Independent Angela Christofilou/The Independent Put It To The People march: Best of The Independent’s pictures Put It To The People protest 23 March 2019 Angela Christofilou/The Independent Angela Christofilou/The Independent Put It To The People march: Best of The Independent’s pictures Put It To The People protest 23 March 2019 Angela Christofilou/The Independent Angela Christofilou/The Independent Put It To The People march: Best of The Independent’s pictures Put It To The People protest 23 March 2019 Angela Christofilou/The Independent Angela Christofilou/The Independent Put It To The People march: Best of The Independent’s pictures Put It To The People protest 23 March 2019 Angela Christofilou/The Independent Angela Christofilou/The Independent Put It To The People march: Best of The Independent’s pictures Put It To The People protest 23 March 2019 Angela Christofilou/The Independent Angela Christofilou/The Independent Put It To The People march: Best of The Independent’s pictures Put It To The People protest 23 March 2019 Angela Christofilou/The Independent Angela Christofilou/The Independent Put It To The People march: Best of The Independent’s pictures Put It To The People protest 23 March 2019 Angela Christofilou/The Independent Angela Christofilou/The Independent Put It To The People march: Best of The Independent’s pictures Put It To The People protest 23 March 2019 Angela Christofilou/The Independent Angela Christofilou/The Independent Put It To The People march: Best of The Independent’s pictures Put It To The People protest 23 March 2019 Angela Christofilou/The Independent Angela Christofilou/The Independent Put It To The People march: Best of The Independent’s pictures Put It To The People protest 23 March 2019 Angela Christofilou/The Independent Angela Christofilou/The Independent Put It To The People march: Best of The Independent’s pictures Put It To The People protest 23 March 2019 Angela Christofilou/The Independent Angela Christofilou/The Independent Put It To The People march: Best of The Independent’s pictures Put It To The People protest 23 March 2019 Angela Christofilou/The Independent Angela Christofilou/The Independent Put It To The People march: Best of The Independent’s pictures Put It To The People protest 23 March 2019 Angela Christofilou/The Independent Angela Christofilou/The Independent Put It To The People march: Best of The Independent’s pictures Put It To The People protest 23 March 2019 Angela Christofilou/The Independent Angela Christofilou/The Independent Put It To The People march: Best of The Independent’s pictures Put It To The People protest 23 March 2019 Angela Christofilou/The Independent Angela Christofilou/The Independent Put It To The People march: Best of The Independent’s pictures Put It To The People protest 23 March 2019 Angela Christofilou/The Independent Angela Christofilou/The Independent

MPs will propose options – expected to include a no-deal Brexit, a customs union, single market membership plus a customs union, a simple free trade agreement and revoking Article 50 – before the speaker whittles them down.

Supporters of a Final Say referendum have tabled a motion insisting no withdrawal deal, or framework for a future relationship, can be ratified “until they have been approved by the people of the United Kingdom in a confirmatory public ballot”.

Votes will be cast on ballot slips, rather than in the traditional way, and MPs can back any number of options, with the results to be declared late on Wednesday.

The idea is to come up with solid ideas, ahead of a second round of voting to produce a winner on Monday – the “group stages before the playoffs”, as one MP put it.

The process was unveiled as:

* The government announced that the blockbuster revoke Article 50 petition, which has gathered a staggering 5.7 million signatures, will be debated next Monday.

* Brexiteer Tories protested that Friday’s agreement with the EU to delay Brexit until at least 12 April had been “unlawful” – ahead of a debate on Wednesday on changing domestic law to accommodate it.

* Andrea Leadsom, the Commons leader, warned MPs’ two-week Easter break from Westminster is likely to be scrapped as the public expected them to be “working flat out”.

Ms May’s departure is being demanded by a growing number of Tories as their price for backing her, so that a new leader can then run crucial trade negotiations with the EU.

The prime minister is still facing another clash with parliament after ministers repeated the threat to ignore any Brexit “plan B” that emerges, if it crosses her red lines.

Sir Oliver said: “We have to use this process tomorrow, and on Monday, to try to work towards a consensus that can carry a majority. That won’t be an easy task. But we owe it to the country to try.”