British Prime Minister Theresa May walks past the EU flag at the conclusion of an EU summit in Brussels, Sunday, Nov. 25, 2018. (AP Photo/Alastair Grant)

London - British Prime Minister Theresa May will on Monday urge lawmakers from all parties to support the Brexit deal she has agreed with the EU, as she also tries to get the public behind the hard-won deal.

"Our duty as a parliament over these coming weeks is to examine this deal in detail, to debate it respectfully, to listen to our constituents and decide what is in our national interest," May will tell lawmakers, according to advance excerpts from her statement.

She said parliament faces a choice between accepting the deal or going "back to square one."

"The British people want us to get on with a deal that honours the referendum," May said, referring to the 52-percent majority vote to leave the European Union in June 2016.

May's minority Conservative government, which has 315 seats in the 650-seat House of Commons - parliament's main, elected house - faces fierce opposition from all sides, with dozens of pro-EU and pro-Brexit Conservatives committed to voting against the deal.

May has appealed to lawmakers from the main opposition party, Labour, to vote for her deal "in the national interest."

But left-wing Labour leader Jeremy Corbyn said he wants the party's lawmakers to oppose the deal, which he called "the result of a miserable failure of negotiation that leaves us with the worst of all worlds."

Influential Conservative right-winger Jacob Rees-Mogg, who leads a group of several dozen eurosceptic lawmakers, said Britain should not be worried about preparing to leave the EU without a withdrawal agreement if parliament rejects May's deal.

Speaking on a phone-in for London radio station LBC, Rees-Mogg accused proponents of the deal of spreading "scare stories" about the risks of rejecting the deal.

The deal includes a temporary, last-resort backstop with slightly different provisions for Northern Ireland from the rest of the United Kingdom.

The Conservative eursosceptics and Northern Ireland's Democratic Unionist Party, whose 10 lawmakers prop up May's government with support on key votes, fear the backstop could become indefinite.

May insists the backstop is unlikely to be needed because she plans to agree a permanent solution for the border during the 21-month transition after Britain leaves the EU in March.

Colum Eastwood, leader of Northern Ireland's moderate Irish nationalist Social Democratic and Labour Party (SDLP), on Monday urged lawmakers from Labour and other parties to back May's deal.

"It is absolutely essential, and we are all saying it... we need you to vote for this deal," Eastwood said, speaking alongside leaders of Irish Republican party Sinn Fein and other Northern Irish parties following talks with business leaders.

Michelle O'Neill, Sinn Fein's leader in Northern Ireland, also said May's deal is "the least worst outcome" and preferable to a no-deal Brexit.

EU leaders endorsed Britain's withdrawal agreement and an accompanying political declaration on future relations on Sunday, after two years of negotiations.

European Commission President Jean-Claude Juncker predicted that it would pass in parliament, despite the strong opposition, adding that it was "the best deal possible for Britain."

Parliament is expected to vote on the deal in mid-December.