Jeremy Corbyn, leader of the United Kingdom's Labour Party, finally moved to back a second referendum on Britain leaving the European Union, if his party fails to get its own version of a Brexit deal passed this week.

Corbyn has said he would favor a public vote to stop British Prime Minister Theresa May's deal being "forced on the country".

The main opposition party was expected to introduce an amendment to its Brexit plan on Tuesday that included the UK staying in a customs union.

Corbyn is not expected to push for a vote on a second referendum until the vote on May's EU exit deal on March 12.

He will first seek to enshrine the Labour party's five Brexit demands in law by proposing an amendment to the government's motion this week. If the plan is rejected, Labour will then support a second referendum.

The party has previously distanced itself from backing a second referendum, and its general election manifesto in 2017 accepted the result of the 2016 vote.

Last week, eight Labour MPs quit the party claiming Corbyn's Brexit policy was a key factor. Some said the Labour leader's latest move is an attempt to stop further defections.

The announcement was met with divided opinion among Labour's own MPs.

Shadow foreign secretary Emily Thornberry told the BBC a second referendum would "break the logjam", while David Lammy, a supporter of the People's Vote campaign for a second referendum, said a public vote would bring a "decisive mandate to move forward".

But Caroline Flint, Labour MP for Don Valley, said the party was in danger of overturning the election promise to respect the 2016 referendum result.

"We can't ignore millions of Labour Leave voters," she said on social media. "There are Labour MPs like me who will not support a second ref."

It is not clear what the proposed referendum would specify, but a briefing paper reportedly given to Labour MPs said any referendum would need to have "a credible Leave option and Remain".

Meanwhile, May will open the way for a delay in Brexit if MPs continue to block the exit deal she is negotiating with Brussels, a move aimed at heading off resignations by about a dozen pro-EU ministers.

After insisting for months that Britain would leave the EU on March 29 without a deal if none could be agreed, the prime minister was on Tuesday expected to offer MPs the chance to take a no-deal Brexit off the table.

The Financial Times has reported that, according to the prime minister's allies, if the House of Commons rejects the renegotiated deal on March 12, May will give MPs another vote on whether to press ahead with a no-deal Brexit on March 29 or to opt for "a short extension" to the Article 50 divorce process.