In a day of drama, May's position seemed suddenly weaker when junior justice minister Phillip Lee, who has always been critical of the government's Brexit strategy, resigned and said he would vote against the government.
Britain's Prime Minister Theresa May returns to Downing Street from the Houses of Parliament in London, Britain, June 12, 2018.
May's fragile government will be trying to defeat a rebellion by pro-EU lawmakers and reverse changes to its key piece of Brexit legislation as the matter comes before the House of Commons for two days of debate.
Ms. May's minority government relies on the support of Northern Ireland's Democratic Unionist Party for a slender working majority in the 650-member Commons.
Parliament must decide whether to support an amendment approved by the House of Lords that could mean sending May back into negotiations with the European Union if lawmakers reject a Brexit deal.More news: P.E.I. premier supports Trudeau trade retaliation
The SNP doesn't have any Lords because of an ideological disagreement with the concept of an unelected upper house - but it does have plenty of MPs in the Commons.
The Lords amendment on a "meaningful vote" for MPs was defeated in the Commons by 324 to 298.
MPs, ministers and officials all agreed Tuesday that a soft Brexit or even the prospect of no Brexit is greatly increased - so too the prospect of a snap early election before the end of the year. An agreement on the Irish border must be reached if there's going to be an overall Brexit deal before the United Kingdom leaves the bloc in March. "How can Boris [Johnson, the foreign secretary] and the ERG [the European Research Group of Euroskeptic MPs] live with this?"
"If we are heading for an impasse in November, everything is on the table".
Brexit Secretary David Davis and Chief EU negotiator Michel Barnier.More news: Kim summit highlights: European Union hails talks as 'crucial and necessary step'
The British government was rocked by a resignation and faced anger in Parliament over its Brexit plans, but staved off defeat by offering concessions to MPs who want to soften the terms of the UK's exit from the European Union. They stood down after the government promised to engage in talks on a compromise.
The Prime Minister is now expected to get through the latest round of crunch Brexit votes unscathed, with a potentially explosive clash over the customs union on Wednesday already defused by a compromise amendment. Wollaston tweeted: "Following further assurances that further govt amendments will come forward in the Lords, I will now be supporting the govt".
"I trust the prime minister". It also attacked the unelected nature of the House of Lords (which traditionally scrutinizes laws passed to it by the elected lower chamber), linking it to a perceived attempt to frustrate the Brexit process.
Following the vote, shadow Brexit secretary Sir Keir Starmer said: "Facing the prospect of a humiliating defeat Theresa May has been forced to enter negotiations with her backbenchers and offer a so-called concession".
The new amendment will be written up at a later stage with detailed plans and concessions.More news: Neymar mocks Austria's 'UFC' tactics after Brazil win