THERESA May must urgently commit to keeping the UK in the European single market and customs union, Scotland’s Brexit Minister had said.

Michael Russell made the call ahead of the Prime Minister asking her Cabinet to sign off her Brexit proposals today.

May will take what is agreed by senior ministers to Florence tomorrow, where she will pitch her vision of Brexit to the other 27 EU leaders.

Reports suggest May will make a “financial offer”, offering to pay a Brexit divorce bill of at least €20bn.

The Tories hope agreeing to pay the money will allow Brussels to agree that substantial progress has been made on negotiations and start work on a trade deal.

The UK Government say the payment will effectively cover what’s due from Britain until 2020, making sure there is no unexpected black hole in the EU’s finances.

“We will at least have something to talk about,” one EU diplomat involved in Brexit said. “But it is not where the landing zone is.”

Russell said there needed to be more, and that any transition should keep the UK in the single market and customs union.

He said: “With just over 12 months left to agree the terms of the UK’s exit from the EU, time is critical.

“The framework for a new relationship still needs to be negotiated and concluded, while companies and public services are finding it increasingly difficult to retain and employ EU workers. The clock is ticking and it is at one minute to midnight.

“We need a transition plan that maintains the UK’s place in the single market and customs union ahead of longer-term European Economic Area and customs union membership.

“As our published proposals make clear, we believe such a framework is feasible and could be agreed in coming negotiating rounds.

“Last December, the Scottish Government set out a proposal for the UK to remain within the single market and to that end to engage in negotiations to secure continued membership of the EEA.

“This will ensure business, and citizens, can be confident they will not face a ‘cliff edge’ exit from the EU in March 2019, and can plan for the long-term.”

The Prime Minister and her Foreign Secretary, Boris Johnson, flew home late last night after attending the UN General Assembly in New York. The two have had a difficult week. Johnson’s 4000 word article in a weekend newspaper outlining his rival Brexit philosophy, undermined his boss, and was widely seen as the first step in his bid to replace May as Tory leader.

Earlier in the week, friends let it be known that Johnson would even resign from government if he didn’t get his way on Brexit.

Johnson, the friends said, “could not live with” a version of Brexit where Britain was still paying hefty sums to Brussels for access to the single market.

Johnson denied the claims, insisting the Cabinet were all “working together”.

“We are a nest of singing birds,” he insisted. “I am mystified by all this stuff. Not me, guv.

“I don’t know where it is coming from, honestly. It feels to me like an attempt to keep the great snore-athon story about my article running. I think that is what is going on.”

Phil Hogan, the Irish European commissioner for agriculture and rural development, said Europe was watching with incredulity the ongoing saga with Johnson and May.

He said: “Clearly, [Johnson] is not directly involved in the negotiations on behalf of the British Government with the EU.

“He certainly has made very strange statements that are completely contradictory, and completely at odds with his own government’s position as well as the possibility of being reasonable with the EU in finalising a deal.

“So it strikes me that he is completely out of the loop in relation to the type of concrete proposals that are required and that are being considered by the UK Government.”

Hogan added: “Johnson is behaving and acting and speaking strangely. It’s clear that his reputation is not good and he is a diminished figure in the Government.”

Hogan also complained about the fact that Johnson’s article failed to mention the Irish border.

He said: “It’s amazing that the UK’s Foreign Secretary can publish a 4000-word article about the UK’s Brexit future and not mention the Irish border.

“You’d think that the Foreign Secretary would have ideas about how to manage the UK’s main land border with the European Union, but obviously not.”