An EU flag flutters during an anti-Brexit demonstration outside the Houses of Parliament in London, Britain January 28, 2019. REUTERS/Hannah McKay

LONDON (Reuters) - Britain’s opposition Labour Party will tell its lawmakers to vote for a plan which could give parliament the power to delay Brexit, a Labour source said on Tuesday.

The move threatens to strip Prime Minister Theresa May of control of the Brexit process unless she is able to agree an exit deal with the European Union that Britain’s parliament will approve.

The Labour instruction relates to a proposal put forward by Labour lawmaker Yvette Cooper which would ultimately give Prime Minister Theresa May until Feb. 26 to agree a Brexit deal. If she is unable to do so parliament would vote on whether to force her to request a delay to Britain’s March 29 exit.

That plan is expected to be put to a vote some time after 1900 GMT, if the Cooper’s proposal is selected for debate by parliament’s speaker, John Bercow.

“We’re backing the Cooper amendment to reduce the threat of the chaos of a no deal exit,” a Labour source said. “The Cooper Bill could give MPs (Members of Parliament) a temporary window to agree a deal that can bring the country together.”

Labour said it would seek to shorten any delay to Brexit, which is currently set at nine months by Cooper. The party’s official support gives the plan a good chance of passing, in what is likely to be a tight vote.

If it does pass, it marks only the first stage in a two-part plan to allow parliament to delay Brexit. The next stage would be for parliament to pass legislation on Feb. 5 which could be used to force the government to ask the EU for more time.