Theresa May has backed down and agreed to publish her plans for Brexit in order to avoid an embarrassing defeat in the House of Commons.

With just moments to go before a Parliamentary deadline, the Prime Minister accepted a Labour motion that she must set out “the Government’s plan for leaving the EU before Article 50 is invoked”.

Labour hailed a “hugely significant climbdown” – immediately demanding that the plan be published “no later than January” next year, to allow for proper scrutiny.

Keir Starmer, the Shadow Brexit Secretary, said: “We have had unnecessary uncertainty, speculation and a running commentary on the Government’s likely approach.

“The Government have now agreed to publish that plan and to do so before Article 50 is invoked. Labour will hold the Government to account on this.”

However, the motion merely requires the Government to publish a “plan” – without stating how detailed that plan must be, let alone requiring a comprehensive white or green paper.

Furthermore, No.10 was confident it had successfully turned the tables on Labour, by adding key words to the motion that mean the party will also be giving its backing to her Article 50 timetable.

Its amendment reads: “That this House should respect the wishes of the United Kingdom as expressed in the referendum on 23 June; and further calls on the Government to invoke Article 50 by 31 March 2017.”

The motion is likely to be agreed without a vote – marking the first time the Commons has given its backing to the policy of triggering Article 50 by that March deadline.

A No 10 source dismissed the idea of a Labour victory, insisting the motion would not force the prime minister to change her approach.

“What it does do is force Labour and Lib Dem MPs who say they support the referendum result to actually do it,” the source said.

And one prominent Tory Leave MP, Steve Baker, said: “I have now seen the Government's amendment for tomorrow and I have seen that it is good. I already feel pro-EU forces deflating.”

However, Jenny Chapman, Labour’s junior Brexit spokeswoman, poured scorn on the idea that the government had “thrown down a gauntlet”.

She tweeted: “Labour won argument for publishing Brexit plan. The Govt's so-called gauntlet more of a soggy mitten as have already said we won't block A50.”

Furthermore, even if MPs vote for Ms May’s amendment, the motion is not binding – so it will not, by itself, trigger Article 50, the EU’s exit notice.

Supreme Court Brexit Challenge Show all 13 1 /13 Supreme Court Brexit Challenge Supreme Court Brexit Challenge People wait to enter the public gallery outside the Supreme Court ahead of the challenge against a court ruling that Theresa May's government requires parliamentary approval to start the process of leaving the European Union, in Parliament Square, central London Reuters Supreme Court Brexit Challenge Gina Miller, co-founder of investment fund SCM Private arrives at the Supreme court in London on the first day of a four-day hearing Getty Supreme Court Brexit Challenge A man waves the EU flag in front of the Supreme Court Getty Supreme Court Brexit Challenge Satirical artist Kaya Mar poses with two of his paintings in front of the Supreme Court Getty Supreme Court Brexit Challenge Pro-Europe protestors dressed as Supreme Court Justices stand outside the Supreme Court ahead of the first day of a hearing into whether Parliament's consent is required before the Brexit process can begin. The eleven Supreme Court Justices will hear the government's appeal, following the High Court's recent decision that only Parliament can trigger Article 50 Getty Supreme Court Brexit Challenge The eleven Supreme Court Justices will hear the government's appeal, following the High Court's recent decision that only Parliament can trigger Article 50 Getty Supreme Court Brexit Challenge Businesswoman Gina Miller arrives at the Supreme Court ahead of the first day of a hearing into whether Parliament's consent is required before the Brexit process can begin Getty Supreme Court Brexit Challenge Attorney General Jeremy Wright arrives at the Supreme Court in London EPA Supreme Court Brexit Challenge Protesters outside the Supreme Court in London, where the Government is appealing against a ruling that the Prime Minister must seek MPs' approval to trigger the process of taking Britain out of the European Union PA wire Supreme Court Brexit Challenge A protesters wearing a judge's wigs and robes stands outside the Supreme Court ahead of the challenge against a court ruling that Theresa May's government requires parliamentary approval to start the process of leaving the European Union, in Parliament Square, central London Reuters Supreme Court Brexit Challenge A protester holds up a placard outside the Supreme Court ahead of the challenge against a court ruling that Theresa May's government requires parliamentary approval to start the process of leaving the European Union, in Parliament Square, central London Reuters Supreme Court Brexit Challenge Pro-Europe protestors dressed as Supreme Court Justices stand outside the Supreme Court Getty Supreme Court Brexit Challenge A man waiting to enter the public gallery waves a European Union flag outside the Supreme Court ahead of the challenge against a court ruling that Theresa May's government requires parliamentary approval to start the process of leaving the European Union, in Parliament Square, central London Reuters

Up to 40 Tory backbenchers were thought to be ready to vote with Labour, amid growing frustration that the Government is keeping MPs in the dark – while leaks to the media about the strategy pile up.

Labour wants the broad aims for Brexit – the Government’s stance on the single market, on freedom movement of EU citizens and on security matters, for example – to be made available.

Ms May had refused to make such a commitment, arguing that “showing the Government’s hand” will weaken its position in the negotiations to follow.

But she was forced to give ground by pro-Remain Tory MPs such as Anna Soubry, who said, of the motion: “I have to say I can't see anything in it I don't approve of and could not support.”

Labour said the need to attract as much Conservative support as possible explained why the motion did not formally demand a white or green paper.

It also acknowledges 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”.

Labour has pointed out that command papers and economic impact papers were put before MPs before Britain entered the then-EEC, in 1973 – arguing for the same.

The Liberal Democrats said Ms May must clear up “the big questions facing the country, including membership of the single market”.