Delayed Brexit looms large as May plans her next move

British Prime Minister Theresa May is planning her next move as the fight over the terms of Brexit continues in parliament and a delay seems increasingly likely.

May is due to present parliament with a revised Brexit plan on Monday after the divorce deal she had struck with the EU was rejected by MPs last week. Source: Press Association

As Prime Minister Theresa May prepares her next move in Britain's deadlocked Brexit battle, a senior opposition politician says it's unlikely the UK will leave the European Union as scheduled on March 29.

A government minister, however, warned that failure to deliver on Brexit would betray voters and unleash a "political tsunami".

May is due to present parliament with a revised Brexit plan on Monday after the divorce deal she had struck with the EU was rejected by MPs last week.

With just over two months until Britain is due to leave the bloc, some members of parliament are pushing for the UK to delay its departure until the country's divided politicians can agree on a way forward.

Labour Party Brexit spokesman Keir Starmer said "it's inevitable" Britain will have to ask the EU to extend the two-year countdown to exit that ends on March 29.

"The 29th of March is 68 days away," Starmer told the BBC on Sunday. "We are absolutely not prepared for it. It would be catastrophic."

May's government is split between ministers who think a disorderly departure must be avoided at all costs and Brexit-backers who believe it would be preferable to delaying or reversing Brexit.

European leaders are increasingly worried Britain will leave the EU without a deal in place. Source: AAP

Former Brexit secretary Dominic Raab, who quit the government in opposition to May's agreement with the EU, said a no-deal Brexit would have "short-term risks" but they would be "manageable".

International Trade Secretary Liam Fox wrote in the Sunday Telegraph that "failure to deliver Brexit would produce a yawning gap between parliament and the people, a schism in our political system with unknowable consequences".

He said public anger could trigger "a political tsunami".

May has been meeting government and opposition MPs in an attempt to find a compromise but there are few signs that she plans to make radical changes to her deal, or to lift her insistence that Brexit means leaving the EU's single market and customs union.

Fox said one possible solution could be to strike a deal with the Irish government guaranteeing there would be no border controls between EU member Ireland and the UK's Northern Ireland.

He said that could ease concerns about the deal's most contentious measure - an insurance policy known as the "backstop" that would keep Britain in an EU customs union to maintain an open Irish border after Brexit.

Pro-Brexit MPs worry that Britain could be trapped indefinitely in the arrangement.

Irish Foreign Minister Simon Coveney, however, tweeted that the Irish government was committed to the entire withdrawal deal, "including the backstop".

British MPs who want a softer Brexit are preparing to try to amend May's plans in a January 29 debate, and to use parliamentary rules to try to prevent a no-deal Brexit and take control of the exit process.

Conservative MP Nicky Morgan said she and several opposition colleagues planned to introduce a bill to ensure "that if the prime minister can't get an agreement approved by the House of Commons by the end of February," the UK will ask the EU to postpone its departure date "so that we can build a consensus and get ourselves more prepared for Brexit".

Starmer said there was a roadblock in the way of a solution to the Brexit crisis, "and that roadblock is the prime minister".

"Her mind is closed," he said.