London - Any request by Britain to leave the European Union later than March 29 would require the approval of all other member states, an EU spokesman said Monday, as British premier Theresa May prepared to make a last-ditch appeal for support for her Brexit plan.

May: No Brexit is more likely

British daily The Guardian reported on Sunday that the EU was preparing to delay Brexit by several months, since it appears highly unlikely that the parliament will approve the divorce deal that May has negotiated with Brussels.

"There has been no UK request for an extension," European Council President Donald Tusk's spokesman, Preben Aamann, told dpa.

"Should there be a UK request to extend, it will be a matter for the EU27 to decide by unanimity," he added, referring to the remaining 27 member states.

Later Monday, May is expected to warn that British lawmakers are more likely to stop Brexit than leave the EU without a deal, the Press Association (PA) reported.

"I ask MPs [Members of Parliament] to consider the consequences of their actions on the faith of the British people in our democracy," May is expected to tell factory workers in pro-Leave Stoke-on-Trent a day before the critical House of Commons vote on her exit plan from the EU.

In a last-ditch appeal for support, the prime minister is expected to warn lawmakers that it's their "duty" to "implement the result of the referendum."

Unregulated Brexit?

Last week, lawmakers narrowly passed a controversial amendment from Conservative former minister Dominic Grieve compelling the government to say within three working days what it will do if, as expected, May's Brexit deal is voted down on Tuesday.

The prime minister will say that she now believes that lawmakers are more likely to block Brexit than allow Britain to exit the EU without a deal.

"What if we found ourselves in a situation where Parliament tried to take the UK out of the EU in opposition to a Remain vote?

"People's faith in the democratic process and their politicians would suffer catastrophic harm," May is expected to say according to a preview of her speech seen by PA.

If lawmakers do not accept May's withdrawal deal and fail to ratify it before March 29, Britain would be on track for an unregulated Brexit.

The European Commission is expected Monday to issue a letter providing Brexit reassurances sought by May to help her get more lawmakers to support her plan.