Andrea Leadsom, chairwoman of the House of Commons and prominent Brexitist, said she could no longer fulfill her duties because she "fundamentally opposes" May's recent Brexit bill.
"I stayed in the Cabinet to fight for Brexit, there were some uncomfortable compromises along the way, but you had my determined support and loyalty in your efforts to make Brexit our common goal," Leadsom said her termination letter to May, which she posted on Twitter.
But Leadsom said she could not find a way forward with the new Brexit deal that May offered on Tuesday. "I no longer believe that our approach will achieve the result of the referendum." Leadsom's resignation could trigger further cuts from the troubled government in May before the Prime Minister's fourth attempt to push through her weakened Brexit deal. A spokesman for Downing Street told reporters, "We are disappointed that it has resigned, and the Prime Minister continues to focus on supporting the Brexit people who have been voted in."
On Twitter, deputy leader of opposition Labor Party Tom Watson described the timing as a "weird" election, just before the European elections.
May is under pressure to resign; If she does that, leadsome is expected to throw her hat in the ring to become the next prime minister.
It would not be the first time. In 201
In her letter, Leadsom pointed out that the latest version of the May Brexit Plan, which allowed legislators to vote on a second referendum as the price to support their deal, was too far-reaching a concession ,
"I have always maintained that a second referendum would be dangerously divisive, and I do not support the government, which willingly allows such a concession," Leadsom said.
In the bid To repackage the plan, May has incorporated him into more comprehensive legislation on the departure of Britain. In addition to offering a second referendum, it also included commitments to workers' rights, environmental protection provisions and a temporary customs relationship with the European Union.
Their "new Brexit deal" has been received by all sides with considerable opposition to the political spectrum. Hardline conservatives who had supported May's recent deal, members of the Democratic Unionist Party (DUP), who support May's minority government in parliament, and supporters of a second referendum all refused.
She did not believe Britain would be "really sovereign".
She was also frustrated with a "collapse of government processes," adding that Brexit legislative proposals had not been "properly audited or approved" by Cabinet members.
It is expected that the Conservative party will be beaten in the European elections starting on Thursday. Leadsom said that on the eve of the vote she had carefully considered the timing of her departure.
"I have carefully considered the timing of this decision, but I can not fulfill my duty as Chair of the House of Representatives tomorrow, a bill with new elements against which I generally oppose," Leadsom said.
The bill on the right of withdrawal in May should be submitted to the lower house in the first week of June.