The breakaway Independent Group of MPs has unveiled its "star candidates2 for European elections, including Boris Johnson's sister and the former BBC presenter Gavin Esler". The country will now not withdraw from the bloc potentially until Oct 31, prolonging the political uncertainty, to the dismay of business leaders.
According to one of May's senior allies, the crucial question for the premier is whether she can sell a compromise on membership of a customs union to her own party, despite her repeated insistence that remaining in the EU tariff regime would be a bad deal.
The Labour MP warned that his party could not "sit on the fence" on such a big issue as Brexit.
Mrs May's official spokesman told reporters: "The Prime Minister said discussions with Labour had been serious but had also been hard in some areas, such as in relation to the timetable for the negotiations".
The new political party, which was formerly the Independent Group, is demanding a second referendum on Brexit.
"We are here to say we stand ready", she said at a launch event in Bristol.
While it would be a non-binding vote, it puts added pressure on the already embattled Prime Minister.
"The problem is not the prime minister, the problem is Brexit", Stewart said.
If it is defeated, it can not be retabled unless the Government brings the parliamentary session to an end and presents a new legislative programme in a Queen's Speech, introducing delays which would nearly certainly dash hopes of avoiding the European elections. Both are likely to be treated as an opinion poll on her leadership.
Under current Conservative Party rules, Tory MPs can not hold another vote of no confidence against Mrs May until December this year.
May's team calculates that while leadership rivals are preparing themselves for a contest to succeed her, potential rivals inside the cabinet do not want to take over until after the United Kingdom has left the EU.
The UK was supposed to finalise its divorce from the European Union on 29 March, but Theresa May's government failed to secure support for its withdrawal agreement before the deadline, which prompted London to request an extension to avoid a no-deal scenario.
May retains hope that she can strike a deal with Labour and get an agreement through Parliament by May 22.