What is really going on in politics? Get our daily email briefing straight to your inbox Sign up Thank you for subscribing We have more newsletters Show me See our privacy notice Invalid Email

Remain MPs believe they have enough support for an amendment to keep Britain in the customs union after Brexit.

Labour's Chuka Umunna confirmed this morning that a cross-party group had proposed clause to implement the trade agreement.

It is the latest threat faced by Theresa May, as the group vowed to force Britain to stay in an EU customs union after Brexit .

The move was proposed in an amendment to the Trade Bill by Tory rebel Anna Soubry.

(Image: Getty)

The clause, put forward by Ms Soubry, Mr Umunna, and Tories Nicky Morgan, Dr Sarah Wollaston, Jonathan Djanogly and Stephen Hammond, reads: "It shall be the objective of an appropriate authority to take all steps to implement an international trade agreement which enables the UK to participate after exit day in a customs union with the EU."

(Image: PA)

Crucially Ms Soubry said she had support from other Remain-backing Tory MPs after she changed the wording from her original amendment which her colleagues were struggling to back.

That means if Labour backed it, MPs could pass the amendment in a humiliating Commons defeat for the Prime Minister.

Labour, whose leader Jeremy Corbyn will give a key speech on Brexit policy this Monday, has not yet said what amendments it will back.

Last night Shadow Foreign Secretary Emily Thornberry confirmed the party wants a customs union that is "pretty much like" what exists now.

(Image: REX/Shutterstock)

Critics say that would ban Britain from signing its own trade deals with countries outside the EU.

Ms Thornberry suggested Britain could get round the problem by negotiating "in partnership" with the EU.

She told LBC: “We would take advantage of being in a partnership with the EU in order to be able to, for example, negotiate with China.

“China wouldn’t just be negotiating with Britain, it would be Britain and the EU."

(Image: AFP)

Ms Soubry tweeted: "I’ve tabled a new amendment to #TradeBill mandating Govt to form "a" Customs Union with #EU #Brexit.

"It's gaining cross party support. It would be in the national interest if the Government & official Opposition also backed it."

A Labour source said: "We don't expect votes on that for quite a while yet and voting decisions would be taken closer to the time."

A second Labour source said the party was still deciding what amendments to back but added: "The government should be worried."

It came as Theresa May held an away day with top Cabinet ministers today in a bid to set Britain's direction after Brexit.

A source told several journalists the idea of diverging from EU rules - which would include the Customs Union - had "won the day".