LONDON — With Britain’s chaotic departure from the European Union just weeks away, three prominent lawmakers abruptly resigned Wednesday from Prime Minister Theresa May’s Conservative Party, saying the government has surrendered control to reckless, hard-line Brexiteers who are endangering the country’s future.

The Conservative members of Parliament who resigned will join a new “Independent Group” of lawmakers formed earlier this week by eight legislators who quit the opposition Labour Party.

The creation of a small but potentially powerful independent bloc of 11 — now composed of moderate rebels from both parties — suggests that seismic forces are at work in British politics. 

These forces have been unleashed by Brexit and the bitter divisions over how and whether to leave Europe behind. Pollsters now report that it is more likely for voters to self-identify as “leavers” or “remainers” than to don traditional party labels.

The three departing Conservatives, who heaped scorn on May for what they called her “disastrous handling of Brexit,” all favor remaining in the European Union. 

At a news conference after their defection, they said others were likely to join them.

While this new Independent Group by itself will not be able to head off Brexit, analysts said, it may play an outsize role in stopping a “no-deal Brexit,” under which Britain would crash out of the continental trading bloc without any transition period or trade deal. 

The defectors left their parties for different reasons, but opposition to Brexit unites them.

The eight centrist members who abandoned Jeremy Corbyn’s Labour Party on Monday and Tuesday said the party has swung too far left. They complained about Corbyn’s handling of Brexit and his inability to stamp out anti-Semitism in the party.

The three Conservatives, or Tories, who broke away on Wednesday blamed their party's “failure” to stand up to zealous Brexiteers, specifically about 60 backbenchers known as the European Research Group, or ERG, who are pushing for a complete break from the European Union. ERG leaders, who have failed to topple May, say they would rather see a “no-deal Brexit” than preserve the relative compromise and closer ties that May seeks on rules and regulations. 

The Tory defectors also complained about the disproportionate power of Northern Ireland’s Democratic Unionist Party, or DUP, which is propping up May’s minority government after her disastrous showing in 2017 snap elections. The DUP — dominated by Protestant loyalists — rejects any compromise that would threaten Northern Ireland’s position in the United Kingdom.

In announcing their resignations, the three Tories — Sarah Wollaston, Heidi Allen and Anna Soubry — told the prime minister in a statement, “We no longer feel we can remain in the Party of a Government whose policies and priorities are so firmly in the grip of the ERG and DUP.”

They wrote: “Brexit has redefined the Conservative Party — undoing all the efforts to modernize it. There has been a dismal failure to stand up to the hard line ERG which operates openly as a party within a party, with its own leader, whip and policy.”

At a news conference, Allen complained that May and the Conservative Party were being “bullied into submission” by hard-line Brexiteers such as former foreign secretary Boris Johnson.

Wollaston said the Conservatives were no longer the “tolerant, moderate, openhearted” party of the past, but have been taken over by the hard right, which she claimed “is marching us toward the cliff edge of a no-deal Brexit.”

Soubry said, “The right-wing, hard-line, anti-E.U. squad are now running the Conservative Party, from top to tail.”  She said this “purple movement” — blending the colors of “two broken parties,” red Labour and blue Conservative — would likely attract more converts and may someday become its own political party  rather than a voting bloc.

“Please, come join us,” Soubry said, predicting that more ministers in May’s cabinet would soon resign their posts — if not their parties — over the prime minister’s handing of Brexit.  

The resignations came before May flew to Brussels for another round of talks on how Britain could leave the E.U. but preserve open borders in Ireland. 

May said she was “saddened” by her colleagues’ decision to leave the party. “These are people who have given dedicated service to our party over many years, and I thank them for it,” she said.

The prime minister acknowledged, too, the obvious, that Brexit is painful and hard. “Of course, the U.K.’s membership of the E.U. has been a source of disagreement both in our party and our country for a long time,” May said. “Ending that membership after four decades was never going to be easy.”

But May said she and the government would press on and deliver the Brexit that the country voted for in a June 2016 referendum. Her Brussels meetings produced no breakthroughs, and the two sides agreed to meet again next week. Corbyn planned to visit Brussels on Thursday for meetings of his own.

Tony Travers, a politics professor at the London School of Economics, noted that the Independent Group now rivals in size the Democratic Unionist Party and Liberal Democrats party.

The new bloc “slightly reduces the power of both the government and the opposition,” Travers said. “It makes an accidental no-deal Brexit fractionally less likely, too.” 

How this changes the dynamics of upcoming votes on Brexit is unclear. It remains possible that Britain will crash out with no deal, or that Britain will seek a delay beyond the March 29 deadline, or that more negotiations will be undertaken, or that citizens will be asked to vote again on whether — now knowing all they know — they really, really want to leave the E.U.

Michael Birnbaum in Brussels contributed to this report.