London (CNN)Theresa May was dealt a significant blow on Wednesday night when one of her top cabinet ministers resigned over the British Prime Minister's approach to Brexit.
Andrea Leadsom quits UK government in fresh Brexit blow for Theresa May
Andrea Leadsom, the Leader of the House of Commons and a prominent Brexiteer, said she could no longer carry out her duties because she "fundamentally opposes" May's latest Brexit bill.
"I stayed in Cabinet to shape and fight for Brexit. There have been some uncomfortable compromises along the way, but you have had my determined support and loyalty in your efforts to deliver Brexit as our shared goal," Leadsom said in her resignation letter to May, which she posted on Twitter.
But Leadsom said she couldn't see a way forward with the new Brexit deal May offered on Tuesday. "I no longer believe that our approach will deliver on the referendum result."
Leadsom's resignation could trigger further defections from May's ailing government ahead of the Prime Minister's fourth attempt to get her beleaguered Brexit deal passed.
May responded that evening with a letter of her own, thanking Leadsom for her service, and saying that she disagreed with her concerns. "I do not agree with you that the deal which we have negotiated with the European Union means that the United Kingdom will not become a sovereign country. If the deal is passed, the UK will leave the European Union," May wrote.
On Twitter, deputy leader of the opposition Labour Party Tom Watson described the timing as an "odd" choice, just before European elections.
May is facing pressure to resign; if she does, Leadsom is expected to throw her hat into the ring to become the next Prime Minister.
It would not be the first time. Back in 2016, Leadsom was in the running against May in the contest to replace David Cameron as leader of the ruling Conservative Party. But May was ultimately selected to lead Britain through its complicated divorce with the European Union. Three years on, May has failed to deliver on the result of the Brexit referendum.
In her letter, Leadsom indicated that the latest version of May's Brexit plan, in which she offered lawmakers the chance to vote on a second referendum as the price for supporting her deal, was a concession too far.
"I have always maintained that a second referendum would be dangerously divisive, and I do not support the Government willingly facilitating such a concession," Leadsom said.
In an attempt to repackage the plan, May rolled it up into a wider set of legislation dealing with Britain's departure. As well as the offer of a second referendum, it also contained pledges on workers' rights, environmental provisions, as well as a temporary customs relationship with the European Union.
Her "new Brexit deal" was greeted with significant opposition from across the political spectrum. Hardline Conservatives who had supported May's last deal, Democratic Unionist Party (DUP) MPs who prop up May's minority government in Parliament and supporters of a second referendum alike all rejected it.
Leadsom said that, with the concessions outlined in May's new deal, she did not believe that the UK would be "truly sovereign."
She also aired her frustrations over a "breakdown of government processes," adding that Brexit-related legislative proposals had not been "properly scrutinized or approved" by Cabinet members.
The Conservative Party is expected to be soundly defeated at the European elections, which begin on Thursday. And Leadsom said that she had thought carefully about the timing of her departure, on the eve of the vote.
"I considered carefully the timing of this decision, but I cannot fulfill my duty as Leader of the House tomorrow, to announce a Bill with new elements that I fundamentally oppose," Leadsom said.
May's Withdrawal Agreement Bill is due to go before the House of Commons in the first week of June.