UPDATE 2-UK opposition Labour says it will back call for second Brexit referendum

Britain's opposition Labour Party said on Monday it would back calls for a second referendum on Brexit if parliament rejects its alternative plan for leaving the European Union. With just over a month until Britain is due to leave the bloc on March 29, Prime Minister Theresa May is seeking changes to her exit deal in order to break an impasse in parliament.

Labour's decision could damage her hopes of winning support for a revised deal in a vote she has promised by March 12, by attracting those who would have backed her agreement to avoid a no-deal exit but who prefer a second referendum. Parliament is due to debate and vote on Wednesday on the next steps in Britain's tortuous departure from the EU, and lawmakers are set to put down proposals, or amendments, which could include demanding the exit deal is put to a public vote.

"We are committed to also putting forward or supporting an amendment in favour of a public vote to prevent a damaging Tory (Conservative) Brexit being forced on the country," Corbyn will tell a meeting of his lawmakers on Monday, his office said. "One way or another, we will do everything in our power to prevent no deal."

Labour said it would put forward an amendment calling on the government to adopt its Brexit proposals, including a permanent customs union with the EU and close alignment with the bloc's single market. "If Parliament rejects our plan, then Labour will deliver on the promise we made at our annual conference and support a public vote," Labour's Brexit spokesman Keir Starmer said on Twitter.

It was not clear whether that support would come at this week's vote in parliament however. A proposal by Labour lawmakers Peter Kyle and Phil Wilson that May's deal be put to the public in another referendum will not be put forward for a vote in parliament until May brings her agreement back for approval.

Labour said it will also support a bid by its lawmaker Yvette Cooper to give parliament the legal power to force May to seek an extension to the Article 50 negotiating period beyond the exit date currently set down in law -- March 29. Corbyn has been under pressure for some time to support a second referendum. Last week, eight referendum-supporting lawmakers quit the Labour Party, in part owing to frustration over his failure to back another vote.

The prospect of holding a second vote poses a dilemma for Corbyn; while many of the party's members and supporters fervently back a so-called People's Vote, others simply want Britain to leave the EU as soon as possible. It remains unclear whether there is a majority in parliament in favour of holding another public vote. (Editing by Kevin Liffey and Catherine Evans)