LONDON — Jeremy Corbyn, the leader of Britain’s opposition Labour Party, announced Monday evening that his bloc in Parliament would support a second referendum to stop what he called “a damaging Tory Brexit.”

While Labour Party activists have been pushing their leader for months to back another public vote on Brexit, Corbyn had been cold to the idea. Many Labour voters — especially in Wales and the north of England — want Britain to leave the European Union.

Corbyn’s shift comes after he was battered by the abrupt resignations of nine Labour lawmakers last week. The defectors, who support remaining in the European Union, complained Corbyn lacked leadership on the greatest issue facing Britain in a generation, and they urged more Labour members to quit.

Corbyn’s late support for a second referendum does not mean another public vote will happen. Prime Minister Theresa May, her government and most of her Conservative Party remain opposed to a do-over.

Nor was it clear Monday what kind of second referendum Corbyn supports. Brexit opponents want voters to be given a clear choice of leaving or staying in the European Union. Others say a second referendum, if it ever took place, should be more limited — asking voters, for example, if they support the deal May has negotiated with the European Union. 

This week will see lawmakers putting forward motions seeking to delay Brexit beyond the scheduled departure date of March 29. Other amendments will try to stop Britain from leaving the European Union with no deal — a scenario that could cause economic chaos.

Corbyn said Monday that Labour would also introduce its own amendment, laying out his party’s alternative deal for a much softer Brexit than May has negotiated with the Europeans. The Labour plan would keep Britain in an E.U. customs regime and single market. Such an arrangement probably would mean that Britain would have to continue to accept the free flow of immigrants from Europe.

Corbyn said that only if Parliament — and the government — rejects Labour’s vision for Brexit would he and his party rally around a second referendum to stop May’s deal.

Conservative Party Chairman Brandon Lewis charged that Corbyn seeks to “betray the will of the British people and ignore the biggest democratic vote in our nation’s history.” Lewis said, “A divisive second referendum that would take us back to square one. Once again, it’s clear: Jeremy Corbyn is using Brexit to play his own political games.”

May spent the weekend in the Egyptian resort of Sharm el-Sheikh, at a meeting of the leaders of European and Arab states, seeking support for additional language to her Brexit deal that would make it palatable to her party. 

Many Conservative Party lawmakers have rejected May’s Brexit deal because it could keep Britain too closely tied to Europe to guarantee that there would be no return of a hard border in Ireland.

While in Egypt, the British prime minister resisted calls to seek a delay for Brexit.

“A delay in this process doesn’t deliver a decision in Parliament, and it doesn’t deliver a deal,” she said at a news conference Monday. “What it does is precisely what the word delay says, it just delays the point in which we come to that decision.”

Corbyn’s spokesman said the Labour leader believes May is “recklessly running down the clock” in an attempt to “force MPs to choose between her botched deal and a disastrous no deal.”

Corbyn’s move toward backing a second referendum was applauded by Labour leaders who don’t like Brexit. Labour lawmaker David Lammy tweeted, “This is a big step towards uniting our party and most importantly our country. No Brexit deal meets the fantasy promised in 2016. So the only way any specific form of Brexit can be made legitimate is through ratification in a #PeopleVote which includes the option to remain.”

London Mayor Sadiq Khan said in a statement that a second referendum would be “the right decision for London — and for the whole country — to give the public their say for the first time on a final Brexit deal. I hope members of parliament will support this move, which is vital to protect jobs and growth. The prime minister must now withdraw article 50 to prevent Britain crashing out of the EU without a deal within weeks and to give us time to sort out her mess.”

Campaigners for a second referendum are hopeful that if the Labour leadership fully lines up behind the cause, they could have a fighting chance at a second vote.

But others said this seemed like a ploy by Corbyn to stop further splits in his party.

Tim Farron, a former leader of the pro-European Liberal Democrats, said, “This is so weak. Or utterly cynical. One or the other.”

Luciana Berger, one of the Labour lawmakers who defected, tweeted, “This. Is. Not. A. New. Announcement. And yet there are just 23 working days to go until #Brexit.”

The Labour Party officially endorsed a second referendum at the party conference in September, but until now it was not fully adopted by Corbyn.

Chris Leslie, another former Labour lawmaker and member of the new Independent Group, said: “Getting Labour to back a People’s Vote has been like extracting blood from a stone. There are no more excuses left — and the question should be put this week without any further prevarication. Let’s wait to see the detail though. We are too used to reading the small print and finding there’s more to this than meets the eye.”

Karla Adam contributed to this report.