Labour and a cross-party alliance are today attempting to seize control of the House of Commons agenda in order to prevent the next Conservative prime minister forcing through a no-deal without the consent of MPs.
Theresa May's former director of legislative affairs, Nikki da Costa, has described the move as "extraordinary".
What are Labour and the cross-party alliance attempting to do?
This evening will be a first step, as the motion essentially asks MPs to vote to hijack the parliamentary timetable from the government in two weeks' time.
On the 25 June, opposition parties will then be able to introduce legislation to bar a prime minister from using prorogation - the suspension of parliament - to force through a no-deal Brexit without the consent of the chamber.
In the absence of any major obstacles, it could become law before the Conservative leadership hustings are over in mid-July and the new PM is installed in Downing Street - constraining their ability to pursue leaving the EU without a deal.
Why are the parties doing this?
As the Tory leadership contest rages on, leadership contenders such as the ex-Brexit secretary Dominic Raab have provoked outrage by suggesting they could prorogue parliament in order to leave the EU in October with, or without, a deal in place.
Esther McVey, the former work and pensions secretary who is also running to replace the prime minister, has not ruled out such a route.
Speaking on Radio 4's Today programme this morning, Jenny Chapman, the shadow Brexit minister, said the vote today is a "safety valve" aimed at Tory leadership contenders attempting to freeze MPs out.
Is it likely to pass?
Labour, the SNP, the Liberal Democrats, the Greens, and Plaid Cymru are all backing the motion, but it is unlikely to pass without support from a fair few Tory backbenchers.
For a short moment, it looked as though cabinet minister Rory Stewart, who is running for the leadership, was willing to back Labour's no-deal motion. But he quickly rowed back, saying he will not be voting for it.
Interestingly, the Conservative MP Sir Oliver Letwin has backed the move and his name even appears on the order paper. This could embolden some Tory MPs to take the unusual step of backing a Labour opposition day motion.
On Tuesday, the shadow Brexit secretary Sir Keir Starmer, said: "MPs cannot be bystanders while the next Tory PM tries to crash the UK out of the European Union without a deal and without the consent of the British people. That's why we are taking this latest measure to end the uncertainty and protect communities across the country.
"My challenge to MPs who disagree either with a no-deal Brexit or proroguing parliament is to back this motion and act in the national interest."
Will this actually stop a no deal?
While it constrains a prime minister's ability to push ahead with a no-deal, it does not prevent a no deal from happening.
It is unlikely - at this stage - but it is still within the power of Brussels to refuse a further extension at the 31 October deadline and opt to break ties with the UK and push ahead without a deal in place.