Britain is more likely to end up leaving the European Union without a deal if parliament rejects the agreement Prime Minister Theresa May has negotiated with Brussels, according to Brexit minister Stephen Barclay.

In an article published on Thursday in the UK's Daily Express newspaper, Barclay, who has been tasked to oversee Britain's departure from the EU bloc, urged MPs to unite behind May's plans ahead of a crucial parliamentary vote.

"No deal will be far more likely if MPs reject the government's Brexit deal later this month," Barclay wrote.

After months of back-and-forth, May struck a widely-criticised withdrawal agreement in November with European leaders, sparking political chaos in the UK and triggering a wave of cabinet resignations.

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"There is obviously division in parliament over the PM's Brexit deal. It’s not a perfect deal. But it's the only workable deal that delivers on the democratic choice of the British people. And it’s the best way to avoid no deal," Barclay said.

British politicians have been unable to agree on any alternative Brexit course, deepening concerns the UK will, as May has warned, drop out of the world's biggest trading bloc without a deal.

MPs are set to vote on the draft agreement in the week beginning January 14.

"My colleagues in Parliament must put the national interest first and vote for this deal so we can get on with delivering Brexit and building the UK’s prosperous future as an outward-looking global trading nation, outside the EU," Barclay wrote in his article.

Brexit chaos

Nearly 52 percent of Britons - more than 17 million people - voted to leave the EU during a divisive referendum held in June 2016. Turnout for the poll was more than 72 percent.

The UK is now set to leave the 28-member bloc on March 29, two years after it triggered Article 50 - the exit clause in the EU's constitution - and kick-started negotiations with European leaders over a divorce deal.

May has rejected growing demands for a second referendum on the UK's membership of the European Union, warning it would "further divide" the country and "break faith" with the British people.

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May's failure to find a deal the British parliament will approve means the world's fifth-largest economy now faces three choices: agreeing on a last-minute deal, halting Brexit, or leaving the EU without an agreement.

No deal means there would be no transition, so the exit would be abrupt.

The deal reached between the UK and the EU allows for a "backstop" to be set up in order to prevent a hard border between Northern Ireland, which is part of the UK, and the Republic of Ireland, an EU member state, if no trade deal is sorted out during the so-called transitional period between 29 March, 2019 and December 31, 2020.

Under the terms of the draft agreement, the whole of the UK will remain in a customs union with the EU "unless and until" the bloc agrees there is no prospect of a return to a hard border.

But the "backstop" idea has prompted scorn from May's parliamentary crutch, the Northern Irish Democratic Unionist Party (DUP), who argue such an arrangement could mean different rules being applied to Northern Ireland than the other parts of the UK.

Hardline Brexiteers within her own Conservative Party, meanwhile, are also unimpressed and have suggested the proposed deal could trap the UK into the customs union forever, effectively forcing it to indefinitely accept EU regulations moving forward.