But she emphasised that neither side wanted this to happen, and repeated that the withdrawal agreement struck with Brussels last month was the only viable option.

“I believe that the deal we have negotiated is a good deal,” she said, adding: “I’m continuing to listen to colleagues on that and considering a way forward.”

May on Tuesday suffered a series of stunning defeats in parliament which threaten her government and ultimately could change the course of Brexit.

She effectively lost her majority in the Commons after the Northern Irish party on which she relies sided with the Labour party to find her ministers in contempt of parliament for failing to publish in full the legal advice on the Brexit deal.

Meanwhile 25 of her own Conservative MPs voted with Labour to give the Commons a bigger say in what happens if, as expected, parliament votes down the Brexit deal on December 11.

The government on Wednesday finally published the six-page advice from the attorney general to the cabinet, which warns of the “legal risk” inherent in a clause intended to keep open the border with Ireland.

It confirms that Britain risks remaining “indefinitely” in the so-called backstop, which could keep the whole country in an EU customs union for years after Brexit, while also keeping the province of Northern Ireland in the bloc’s single market.

MPs on Tuesday also voted to approve an amendment tabled by Conservative former attorney general Dominic Grieve, which allows parliament to determine what happens if the deal falls.

If May loses the vote next week, the government has 21 days to return to MPs to propose what happens next.

Grieve’s amendment could allow MPs to amend that statement, raising the possibility they could demand a re-negotiation, a second referendum or even staying in the EU.

International Trade Secretary Liam Fox aired that concern, saying that a majority in parliament in favour of staying in the EU “may attempt to steal Brexit from the British people”.

May opened the first of five days of debate on the Brexit deal on Tuesday evening and Wednesday’s discussion was to focus on security.

On Tuesday, opposition Labour leader Jeremy Corbyn called May’s plan “a huge and damaging failure for Britain”.

Going around in circles

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But May warned on Tuesday that another Brexit vote would do nothing to settle the bitter domestic debates about Britain’s place in Europe that have raged since it joined the bloc in 1973.

“We cannot afford to spend the next decade as a country going around in circles,” she argued.

Many MPs want May to return to Brussels to renegotiate her deal, and she is scheduled to attend a summit meeting two days after next week’s vote. However, EU leaders have repeatedly said they will not reopen the divorce deal.

In Brussels, the European Commission on Wednesday began the process of ratifying the Brexit deal.

European Commission Vice President Valdis Dombrovskis told reporters: “We are preparing for the deal”.

Other MPs are pushing for Britain to stay in the European Economic Area (EEA), which would protect the economy but would not fulfil the referendum promise of ending free movement of workers from the EU.

Some Eurosceptic Conservatives believe that Britain could leave without any deal at all, although a government assessment last week found this risked causing a major recession.

If her deal fails, May would likely face a confidence vote in the Commons, or a challenge by her own Conservative MPs.