Theresa May says she is "ambitious" about trade negotiations with the EU, as she faces a damaging Tory rebellion in a Commons debate on the Government's Brexit plans.

A Labour motion, to be debated on Wednesday, calls on the Prime Minister to commit to publishing the Government's plan for leaving the EU before Article 50, the formal process for leaving, is invoked.

One leading pro-Remain Conservative MP, Anna Soubry, has predicted the number of Tory MPs who will vote for the Labour motion will be at least 20, enough to defeat the Government.

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Ms Soubry, a former minister, said Labour's motion was "eminently supportable", adding: "This transcends party politics and tribalism. I have to say I can't see anything in it I don't approve of and could not support."


And she told The Guardian: "I would expect at least 20 of my colleagues to vote for it. People are very concerned. We are getting a running commentary. We need clarity."

Veteran former Cabinet minister and leading pro-European Ken Clarke has said he intends to vote for the Labour motion.

"I plan to support the Labour motion on Article 50 in what appears to be its current form," he told The Independent.

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Ahead of a similar vote in October, on a motion that also said MPs should "properly scrutinise the plan for leaving the EU before Article 50 is invoked", the Prime Minister was forced into a last-minute climbdown.

The Government tabled an 11th-hour amendment which accepted Labour's motion, as long as scrutiny in Parliament did not "undermine" the negotiation.

This time, in an attempt to woo Tory rebels, Labour's carefully worded motion says "there should be no disclosure of material that could be reasonably judged to damage the UK in any negotiations to depart from the European Union after Article 50 has been triggered".

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Shadow Brexit secretary Sir Keir Starmer said: "Labour accept and respect the referendum and we will not frustrate the process of leaving the EU.

"But Parliament and the public need to know the basic terms the Government is seeking to achieve from Brexit. This issue is too important to be left mired in uncertainty any longer.

"That is why Labour have called this debate on Wednesday.

"Our motion is simple but would deliver real accountability and grip in the Brexit process. I hope MPs on all sides of the House will join Labour in supporting it."

But earlier the Prime Minister's official spokeswoman claimed Labour "want to frustrate the will of the people by slowing down the process of leaving and trying to tie the Government's hand in the negotiation".

A spokesman for the Labour leader Jeremy Corbyn hit back: "Labour respects the decision of the British people to leave the European Union and supports the invoking of Article 50.

"But the Government must first of all bring its opening negotiating terms to Parliament for scrutiny.

"It is about to enter into the most significant set of negotiations this country has faced for decades, and the British people must first have sight of the Government's plan, if indeed it has one."

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As the European Union's chief Brexit negotiator Michel Barnier warned on Tuesday of the "complicated" negotiation path ahead, Theresa May said she would push for the "right deal" during talks for allowing the UK to stay in the single market.

Speaking during an official visit to Bahrain, she said she was "ambitious" about what could be achieved during trade negotiations.

:: Labour's motion reads: "That this House recognises that leaving the EU is the defining issue facing the UK;

:: "Notes the resolution on parliamentary scrutiny of the UK leaving the EU agreed by the House on 12 October 2016;

:: "Recognises that it is Parliament's responsibility to properly scrutinise the Government while respecting the decision of the British people to leave the European Union;

:: "Confirms that there should be no disclosure of material that could be reasonably judged to damage the UK in any negotiations to depart from the European Usunion after Article 50 has been triggered;

:: "And calls on the Prime Minister to commit to publishing the Government's plan for leaving the EU before Article 50 is invoked."

:: Watch full coverage of the Government's Article 50 challenge at the Supreme Court on Sky News. There will also be a special programme including highlights from the second day of this historic challenge at 9.30pm on Sky News.