Brexit timetable thrown into turmoil as Theresa May is forced to cancel planned cabinet meeting to approve her deal

Hopes fading for an EU sign off this month amid fierce resistance to the PM’s proposals in her cabinet and in Brussels

Theresa May has been forced to abandon plans for an emergency cabinet meeting to approve a Brexit deal, after fresh opposition at home and abroad plunged her timetable into turmoil.

The prime minister shelved the meeting, pencilled in for Monday, slamming on the brakes after fierce resistance in her cabinet and in Brussels threatened to derail the path to an agreement.

A government source conceded that an outline deal might not be ready by Tuesday – making it increasingly unlikely that a special EU summit to sign it off can be held in November, as hoped.

That would leave the UK having to ramp up hugely expensive no-deal preparations and in danger of being unable to pass all necessary legislation before the Brexit deadline next March.

At home, Ms May faced an open challenge to her plans from Andrea Leadsom, the Commons leader, who vowed the UK “cannot be held against its will” by the backstop plan for the Irish border.

Ms Leadsom became the second cabinet minister to insist on a unilateral power to escape being bound in the EU customs union – something explicitly ruled out by Brussels.

In the Belgian capital, talks between UK and EU officials hit a wall over how to terminate the backstop, with fishing rights another key obstacle.

Meanwhile, there was fresh confusion over Labour’s stance on a Final Say referendum on the Brexit outcome – with Emily Thornberry, the shadow foreign secretary, directly contradicting Jeremy Corbyn.

Cabinet ministers had been told to “clear their diaries” for an “approve the deal” meeting at the end of last week, a get together then put back until Monday.

But, the source told The Independent: “There is not going to be one tomorrow.”

They added: “The cabinet will meet as normal on Tuesday, but I can’t say if it going to be a Brexit cabinet or not, because the negotiations are ongoing.”

The source acknowledged the delay, but said: “The fact is that we have got to get something that’s right. We are not going to accept an outline deal at all costs and we are still working on it.”

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.

The continued turmoil burst out into the open when Ms Leadsom told BBC Radio 5 Live: “The UK cannot be held against its will in a customs arrangement.”

The prime minister has urged her cabinet to abandon hopes of a unilateral power to end the backstop and push for a joint review mechanism with Brussels instead.

But pro-Brexit Tories fear the UK will locked indefinitely into the customs union – unable to sign its own trade deals – unless it can end the backstop unilaterally, at some point soon after 2020.

Ms Leadsom said: “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 she warned: “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 came days after Liam Fox, the international trade secretary, also insisted the power must rest with “the sovereign British government”.

Ms Leadsom also rejected the idea of an independent body to review if an alternative solution has been found to avoid checks at the Irish border – something 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.”

Crucially, the EU is 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 the prime minister also makes that concession – after repeatedly ruling out ECJ jurisdiction – she would risk even greater opposition on the Tory benches.

Ms Thornberry sought to calm Labour tensions by saying the party could still back a Final Say Brexit referendum, just a day after her leader rubbished the idea.

The shadow foreign secretary said “all options remain on the table” if Labour fails to force a general election by voting against the deal, if there is one.

Mr Corbyn has angered Labour MPs and supporters by arguing Brexit cannot be stopped – and by going on to reject the growing calls for a fresh public vote.

But Ms Thornberry said: “If we don’t have a general election then, yes, of course all the options remain on the table and we would campaign for there to be a people’s vote – but there are several stages before we get that.”