Oliver Letwin, the former Tory minister leading efforts in Parliament to block a no-deal Brexit, said he’s confident he has a plan that will work around Boris Johnson’s move to suspend Parliament, as former Prime Minister John Major announced he will join a court case against his successor.

Letwin said he’s been talking to Speaker of the House of Commons John Bercow about possible maneuvers. While he didn’t go into detail, it’s likely to involve requesting an emergency debate when Parliament returns on Sept. 3, and then using that to take control of the agenda.

“I know there are a number of my colleagues who feel as I do that a disorderly no-deal Brexit is a very bad idea,” Letwin told the BBC. “I hope that Parliament will take a series of actions in a proper, orderly way that by the end of the week mean that Boris Johnson knows that as prime minister he has backing of many, many of us to get a deal but that if he doesn’t get a deal he’s going to have to seek an extension.”

The prime minister caused outrage this week when he announced Parliament will be suspended from Sept. 12 to Oct. 14. Although he argued it was a necessary move to allow him to press on with his domestic agenda, the effect will be to limit the time his opponents have to stop Britain leaving the European Union without a deal, something they say would be an economic catastrophe.

Major, who campaigned to stay in the EU, said he will apply to join a court action brought by Gina Miller in London challenging the legality of the prime minister’s decision. While the two men come from different factions in the Conservative Party, being challenged by such a senior figure is potentially embarrassing for Johnson.

“I promised that, if the Prime Minister prorogued Parliament in order to prevent Members from opposing his Brexit plans, I would seek judicial review of his action,” Major said in statement. “I intend to seek to assist the Court from the perspective of having served in Government as a Minister and Prime Minister, and also in Parliament for many years as a Member of the House of Commons.”

A Scottish judge refused to grant an emergency injunction against Johnson’s plan on Friday, saying there is more time for hearings on the issue next week, setting up a frantic week of court proceedings in Edinburgh, London and Belfast starting on Tuesday.

Letwin told the BBC he believes there “probably” is still time to act in Parliament, so long as lawmakers are ready to vote with him.

Even with the support of the Democratic Unionist Party, Johnson has a majority of just one in the House of Commons, and opposition parties are united against a no-deal Brexit, meaning the numbers are not in his favor. Former Conservative ministers, including Chancellor of the Exchequer Philip Hammond, have attacked Johnson’s move to suspend Parliament and have said they’re prepared to vote to block leaving without an agreement.

The problem facing any move against the government in Parliament is that the timetable of the chamber is controlled by ministers, which is why Letwin and his allies will need to win a vote allowing rank-and-file lawmakers to take control of the agenda.

Lawmakers from across the political spectrum have been working together on plans to take action when Parliament reconvenes after its summer recess on Tuesday and John McDonnell, economy spokesman for the opposition Labour Party, said he’s also “increasingly confident” that a majority can be found to block a no-deal divorce.

“The key thing is next week and whether we can get legislation or other measures through Parliament,” McDonnell said in an interview with Bloomberg TV on Thursday. “It’s going to be difficult, but I’m hoping that with the commitment we’ve seen we will succeed.”

A bigger problem could come in the upper House of Lords, where any new law will also have to be passed. Although there are certainly the votes there against a no-deal Brexit, there are fewer rules to stop measures being filibustered or delayed by members talking at excessive length.

However Shami Chakrabarti, who speaks on legal matters for the opposition Labour Party in the Lords, said that “of course” the chamber would be willing to sit over the weekend if necessary.