Prime Minister Theresa May has suffered another Brexit defeat after the House of Commons on Thursday rejected a motion seeking endorsement for her Brexit plans.

MPs voted 303 to 258 to reject the government's motion after dozens of pro-Brexit MPs abstained.

Some Brexit advocates argued that the motion would have effectively ruled out a no-deal Brexit.

May had asked MPs to send a "clear message" to the European Union.

It is the eighth time the government has lost a House of Commons vote on Brexit.

LONDON — Prime Minister Theresa May has suffered another Brexit defeat in the House of Commons after rebel Conservative MPs abandoned their support for her plans to break from the European Union.

The prime minister had asked MPs to send a "clear message" to the EU about their desire for "legally binding changes" to her Brexit deal, with the UK's scheduled exit just weeks away.

But in another day of Westminster drama, MPs voted 303 to 258 on Thursday evening to reject the prime minister's motion seeking endorsement for her plan to renegotiate the controversial backstop for Northern Ireland.

A majority of Conservative MPs in the pro-Brexit European Research Group abstained from the vote, leading May's government to its eighth Brexit defeat in the House of Commons.

A Downing Street spokesperson said: "While we didn't secure the support of the Commons this evening, the Prime Minister continues to believe, and the debate itself indicated, that far from objecting to securing changes to the backstop that will allow us to leave with a deal, there was a concern from some Conservative colleagues about taking no deal off the table at this stage."

The prime minister's opponents called on her to change course.

"Tonight's vote shows there is no majority for the prime minister's course of action on Brexit," the Labour Party's leader, Jeremy Corbyn, told MPs immediately following the vote.

"Yet again she has been defeated. The government cannot keep on ignoring parliament."

David Lammy, a Labour MP who supports the anti-Brexit Best For Britain campaign, described the result as a "massacre for the government and a damning indictment of the Prime Minister's Brexit plan."

He added: "The Prime Minister has nowhere left to hide.

"Her threats to throw the country off a cliff edge if MPs do not vote for her deal will be exposed as deeply cynical by a leader more concerned with the future of her party than her country. She should now rule out no-deal and put her deal to a public vote with the option of remaining in the EU."

Thursday's vote wasn't legally binding, but it had symbolic weight and puts even greater pressure on May to change her Brexit strategy.

The vote was originally expected to be a straightforward victory for the government as it sought a repeated endorsement for a motion previously passed by MPs two weeks ago.

But dozens of pro-Brexit MPs abstained on the prime minister's motion, as they believed it also endorsed a previous amendment that called on the government to rule out a no-deal Brexit.

Brexit Secretary Stephen Barclay had insisted in the Commons that a no-deal Brexit was still possible. Conservative rebels accused the government of "doublethink," however, after ministers refused to rewrite their motion.

"We're now truly entering the world of George Orwell's Ministry of Truth," Conservative MP Bill Cash told the Commons.

"In his book 1984, Orwell said doublethink means the power of holding two contradictory beliefs in one's mind simultaneously and expecting both of them. This double motion is doublethink in action and I cannot possibly vote for it."

Pro-Brexit MPs were split on whether to back the prime minister, with some members of the ERG breaking to back May's motion.

The result means the prime minister will return to Brussels later this month without the clear support from Parliament for a renegotiated deal.

It will also add to growing pressure on May to shift towards backing a customs union with the EU to win support from Labour and other opposition parties.