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A second cabinet minister has rejected a key plank of Theresa May ’s Brexit plan, raising the prospect of fresh resignations if she tries to force it through.
Andrea Leadsom , the Commons leader also warned the proposal – giving the EU a joint say over when the UK can break free of the Irish border “backstop” – would be thrown out by parliament.
The prime minister has urged her cabinet to accept they must abandon hopes of a unilateral power to end the backstop and push for a joint review mechanism with Brussels.
But Ms Leadsom told BBC Radio 5 Live: “The UK cannot be held against its will in a customs arrangement.
“It must be capable for the United Kingdom to decide to leave that customs arrangement and it cannot be something that the European Union can then hold us to.
“And, frankly, it’s because that would be to then fail to fulfil on the will of the people expressed in the referendum and I very much doubt that we would get it through parliament.”
The warning comes days after Liam Fox , the international trade secretary, also insisted the power must rest with “the sovereign British government” .
At stake is the fear of pro-Brexit Tories that the UK risks being locked indefinitely into the EU customs union – unable to sign its own trade deals – unless it can end the backstop unilaterally.
A historic moment: thousands march to demand Final Say on BrexitShow all 65 1 /65A historic moment: thousands march to demand Final Say on Brexit A historic moment: thousands march to demand Final Say on Brexit An estimated 700,000 people marched through London to demand a final say on the withdrawal agreement
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit Red smoke from a canister hangs in the air as around 100,000 demonstrators march through London during a People's Vote anti-brexit demonstration savings banners and placards Anti-Brexit People's Vote March for the Future in London
Rex
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit Mayor of London Sadiq Khan takes part in the People's Vote March for the Future in London, a march and rally in support of a second EU referendum.
PA
A historic moment: thousands march to demand Final Say on Brexit Final Say campaigners take part in the peoples vote march for the future in London 20/10/2018 Protesters wearing final Say shirts and holding placards
Angela Christofilou
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit MP Chuka Umunna (left) and MP Vince Cable (right) as MP Anna Soubry (centre) addresses Anti-Brexit campaigners at a rally after the People's Vote March for the Future in London, a march and rally in support of a second EU referendum.
PA
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit A People’s Vote march attendee calls for a Final Say
Angela Christofilou
A historic moment: thousands march to demand Final Say on Brexit Demonstrators with banners 'We're with EU' during the People's Vote March for the Future in London, Britain, 20 October 2018. Reports state that the 'March for the Future' is to be led by a column of young people and call for a People’s Vote on the Brexit deal. After marching through central London, there will be a rally on stage in Parliament Square, including speeches from Mayor of London Sadiq Khan.
EPA
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit Protesters at London’s march for the future in October
The Independent
A historic moment: thousands march to demand Final Say on Brexit Editor of The Independent Christian Broughton speaks to demonstrators in Parliament Sqaure after they take part in a march calling for a People's Vote on the final Brexit deal, in central London on October 20, 2018. - Britons dreading life outside Europe gathered from all corners of the UK to London on Saturday to try to stop their country's looming breakup with the EU.
AFP/Getty
A historic moment: thousands march to demand Final Say on Brexit A poster at the March for the Future in October
The Independent
A historic moment: thousands march to demand Final Say on Brexit Anti-Brexit campaigners take part in the People's Vote March for the Future in London, a march and rally in support of a second EU referendum.
PA
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit Final Say campaigners take part in the peoples vote march for the future in London 20/10/2018
Angela Christofilou
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit Anti-Brexit campaigners take part in the People's Vote March for the Future in London, a march and rally in support of a second EU referendum.
PA
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit Demonstrators hold placards as they take part in a march calling for a People's Vote on the final Brexit deal, in central London on October 20, 2018. - Britons dreading life outside Europe gathered from all corners of the UK to London on Saturday to try to stop their country's looming breakup with the EU.
AFP/Getty
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou
A historic moment: thousands march to demand Final Say on Brexit Final Say campaigners take part in the peoples vote march for the future in London 20/10/2018 campaigner wrapped in EU flag
Angela Christofilou
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit
Angela Christofilou/The Independent
A historic moment: thousands march to demand Final Say on Brexit Final Say campaigners take part in the peoples vote march for the future in London 20/10/2018
Angela Christofilou
A historic moment: thousands march to demand Final Say on Brexit Demonstrators pass Trafalgar Square as they take part in a march calling for a People's Vote on the final Brexit deal, in central London on October 20, 2018. - Britons dreading life outside Europe gathered from all corners of the UK to London on Saturday to try to stop their country's looming breakup with the EU.
AFP/Getty
A historic moment: thousands march to demand Final Say on Brexit Demonstrators wave Union and European flags and hold up placards as they pass Trafalgar Square, taking part in a march calling for a People's Vote on the final Brexit deal, in central London on October 20, 2018. - Britons dreading life outside Europe gathered from all corners of the UK to London on Saturday to try to stop their country's looming breakup with the EU.
AFP/Getty
A historic moment: thousands march to demand Final Say on Brexit Demonstrators hold placards as they take part in a march calling for a People's Vote on the final Brexit deal, in central London on October 20, 2018. - Britons dreading life outside Europe gathered from all corners of the UK to London on Saturday to try to stop their country's looming breakup with the EU.
AFP/Getty
A historic moment: thousands march to demand Final Say on Brexit A demonstrator holds a message during a march calling for a People's Vote on the final Brexit deal, in central London on October 20, 2018. - Britons dreading life outside Europe gathered from all corners of the UK to London on Saturday to try to stop their country's looming breakup with the EU.
AFP/Getty
A historic moment: thousands march to demand Final Say on Brexit Anti-Brexit campaigners take part in the People's Vote March for the Future in London, a march and rally in support of a second EU referendum.
PA
A historic moment: thousands march to demand Final Say on Brexit Demonstrators take part in the 'People's Vote March for the Future,' in central London, Britain, 20 October 2018. Reports state that the 'March for the Future' is to be led by a column of young people and call for a People’s Vote on the Brexit deal. After marching through central London, there will be a rally on stage in Parliament Square, including speeches from Mayor of London Sadiq Khan
EPA
A historic moment: thousands march to demand Final Say on Brexit A protester brandishes an Independent t-shirt during the Brexit March
Angela Christofilou
A historic moment: thousands march to demand Final Say on Brexit Anti-Brexit campaigners take part in the People's Vote March for the Future in London, a march and rally in support of a second EU referendum
PA
A historic moment: thousands march to demand Final Say on Brexit Tens of thousands of people take part in People's Vote March for the Future in central London. The march organised by the People's Vote campaign is led by young people calling for a People's Vote on the Brexit deal
Rex
A historic moment: thousands march to demand Final Say on Brexit Anti-Brexit campaigners take part in the People's Vote March for the Future in London, a march and rally in support of a second EU referendum
PA
Ms Leadsom also rejected the idea of an independent body to review if an alternative solution has been found to avoid Irish border checks – something currently dependent on untested technology.
However, she insisted she was not on the verge of resigning, saying: “I’m sticking in the government to make sure that’s where we get to in the end.”
The Commons leader also dismissed suggestions that she was expecting other ministers to quit, adding: “No I’m not. That was a great surprise to me that he [Jo Johnson ] resigned.
Nevertheless, the cabinet fightback means the prime minister’s hopes of agreeing an outline deal with her cabinet as early as tomorrow appear to be fading.
Senior ministers are also demanding to see full legal advice on the power to be conceded over ending the backstop, after Ms May indicated only a legal summary would be made available.
Meanwhile, EU leaders have also warned that crucial obstacles remain over how to settle future disputes over the Irish border and also over fishing rights.
Crucially, they are believed to have rejected Britain’s proposal of independent arbitration over ending the backstop, insisting the European Court of Justice must make the decision.
If an outline deal is not agreed by the middle of this week, it is unlikely that an emergency summit to sign it off can be held in November – throwing back a final agreement until the middle of December.
That would leave the UK having to ramp off hugely-expensive no-deal preparations and in danger of being unable to pass all necessary legislation before Brexit day next March.
Damian Hinds , the education secretary, warned cabinet rebels that the EU would not accept the UK being able to end the backstop.
“If you have too hard a line about saying, 'well we must just have a totally unilateral exit, or there's an absolutely fixed, hard end date', that is very, very unlikely that is going to be negotiable with the other side,” he admitted.
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