Brexit Secretary David Davis has warned Conservative Party rebels that proposals to give Parliament the power to direct negotiations with the European Union are simply a tactic to overturn the results of the 2016 referendum that mandated Britain's departure from the bloc.
The House of Commons voted 324 to 298 to defeat an amendment to the EU (Withdrawal) Bill which would have removed her government's power to unilaterally walk away from talks with Brussels.
The main point of contention between those who want to keep the closest possible ties with the European Union and those who aim for a clean break is a demand to give parliament a "meaningful vote" on any agreement May negotiates with Brussels.
Passions ran high in Tuesday's three-hour debate, when angry eurosceptics accused their rivals of trying to undermine the 2016 referendum vote to leave the EU.
Fellow MP Antoinette Sandbach rejected suggestions by leading Brexiteers in her party that this would tie the prime minister's hands in negotiations.
It's been revealed ex-Tory ministers Ken Clarke and Anna Soubry rebelled against the government by voting against the motion to disagree with Lords amendment, created to give Parliament a vote to prevent a "no deal" Brexit.
Seeking to placate would-be Conservative rebels, government frontbenchers offered to meet them to discuss their concerns, and agreed to "engage positively" on a "compromise" put forward by one of them, former attorney general Dominic Grieve.
The government has been criticised for not allowing time to debate the Irish border during a series of key Brexit votes at Westminster.
In a highly charged atmosphere in parliament, lawmakers who oppose the government said they had received death threats and brandished a copy of one of Britain's tabloid newspapers, the Daily Express, which ran a headline saying: "Ignore the will of the people at your peril". "It enables parliament to dictate to the government their course of action in global negotiations".
The Bracknell MP, who called for a second referendum on whatever deal Mrs May secures from the European Union, later told the Commons there was growing evidence that the Government's Brexit policy is "detrimental to the people we were elected to serve".
Speaking on BBC Newsnight, Mr Grieve commented on the Government's concessions, stating: "There was bound to be discussion about the amendment, and that discussion was positive".
"I can not support the government's decision to oppose this amendment because doing so breaches such fundamental principles of human rights and parliamentary sovereignty", he said.
Which side won on Tuesday will become much clearer in the next few days, when the government amendment is tabled in black and white.
The Democratic Unionist Party has said it will be supporting the government in the votes.
"We are asking members of parliament to abide by the referendum result, our manifesto commitment and to back our country", Andrew Bridgen, Conservative lawmaker and Brexit campaigner, told Reuters.
Earlier May suffered a setback when junior justice minister Phillip Lee, who has always been critical of Brexit strategy, resigned and said he would vote against the government.
"Ultimately, it is very likely that this amendment will come back from the House of Lords and will be reconsidered".
Commenting after Tuesday's votes, Dr Lee said: "Delighted that the government has agreed to introduce an amendment to the EU Withdrawal Bill which will give Parliament the voice I always wanted it to have in the Brexit process".
A Commons defeat on the issue would have been a significant blow to May's authority and risked triggering a leadership crisis for the prime minister.