Opponents of UK Prime Minister Boris Johnson submitted legislation on Tuesday to possibly extend the Brexit process by another three months.
Rebel ruling party lawmakers and opposition MPs were later set to meet the parliamentary speaker, seeking to seize the voting agenda from the government.
Read more: Brexit: EU's top negotiator doubts no-deal can be avoided
That would allow them to vote on the bill, which would force Johnson to seek a Brexit extension until January 31, 2020, should no new deal emerge at an EU summit in mid-October.
The UK's former Finance Minister Philip Hammond — one of the Conservative rebels — said he was confident of defeating the government.
"There will be enough people for us to get this over the line," Hammond predicted in an interview with the BBC.
Johnson took office in July with a promise to take Britain out of the EU on October 31, with or without a deal, as his key pledge to the Conservative Party members who elected him. Any extension would be politically damaging — enraging Euroskeptic hardliners within the party.
The prime minister has said he wants an amicable divorce with Brussels but has rejected the exit terms on offer — in particular, the Irish backstop.
The bill was submitted as Britain's lower house of parliament returned from summer recess. Those backing it include former Tory ministers, as well as the Labour Party, the Scottish National Party, and the Liberal Democrats. Proponents of the legislation say the possibility of no-deal should not be entertained, claiming it would result in economic calamity for the UK.
Read more: Facebook returns to center of British politics
On Monday night, Johnson warned rebellious Tory MPs that a bill to prevent no-deal would "chop the legs" out from under the UK's negotiating position. The prime minister hinted that he might be forced to call a general election, should the vote go against him.
Details of the opposition's draft legislation to prevent no-deal emerged on Monday afternoon, in a tweet from opposition Labour Party MP Hilary Benn.
Meanwhile, the European Commission said that, while it still hoped for an agreement, it was preparing for the possibility of a no-deal Brexit.
"Whether it is the most likely scenario... I would say it is a very distinct possibility, which is precisely why we launch this final call to be prepared in case a no-deal Brexit occurs," said Commission spokeswoman Mina Andreva.
Andreva said an agreement based on the deal agreed with former UK Prime Minister Theresa May would be preferable. However, Parliament has already rejected the May deal on three separate occasions.