In the UK, Conservative MPs are meeting to consider a rule change, which could allow another confidence vote in Theresa May.
There are also rumours of a row in her own top team over the British Prime Minister's new Brexit offer.
At least one minister has asked for a meeting with her this evening - some in her Cabinet could be prepared to tell her to go.
UK Labour MP Rosie Duffield said she has seen members of the Conservative Party "actually running along corridors" in Parliament, adding there is "big news expected" tonight.
She tweeted: "Members of Parliament from a certain Tory faction actually running along corridors.
"Lots of rumours flying around. Big news expected tonight... #EndOfDays?"
Tory MP Tom Tugendhat, chairman of the Commons Foreign Affairs Committee, said he too now believed the Prime Minister must go.
Writing in the Financial Times he said that was the only way to avoid a no-deal Brexit.
"There is one last chance to get it right and leave in an orderly fashion," he wrote.
"But it is now time for Prime Minister Theresa May to go - and without delay.
"She must announce her resignation after Thursday's European elections. And the Conservative party must fast track the leadership process to replace her."
The executive of the 1922 Committee are to meet with the chief whip at 5.30pm, sources said.
Tory MPs will then join the meeting at 6pm.
Tory MP Mark Francois, leaving the meeting of the 1922 committee said: "If I were a betting man, I'd bet £50 for Help for Heroes that the second reading of the WAB will never ever happen and I invite another colleague, whoever it may be, to take my bet."
