DOWNING Street has denied the UK Cabinet’s agreed back-stop option to guarantee a soft border between Britain and the EU post-Brexit is a “fudge” as Brussels was quick to question whether it would work.

After weeks of internal negotiations and even suggestions of a threatened resignation from David Davis, Theresa May finally got agreement with her Cabinet’s leading Brexiteers.

This followed three separate early morning meetings in her Commons office with Mr Davis and his colleagues Boris Johnson and Liam Fox, which were described as “constructive”. No 10 made clear none of them had threatened to resign.

Asked if the Prime Minister was confident Brussels would accept the “fudged” back-stop plan, her deputy spokeswoman said: “I wouldn’t recognise that word but it’s important to say the EU put forward their proposal and we were clear…that was unacceptable; this is our counter-proposal. We look forward to discussing it further with the EU.”

As the so-called Brexit War Cabinet later met in Downing Street, before Mrs May jetted off for the G7 summit in Canada, the Government published its technical note on its back-stop plan.

The key lines were: “The UK is clear the temporary customs arrangement, should it be needed, should be time-limited and that it will be only in place until the future customs arrangement can be introduced…The UK expects the future arrangement to be in place by the end of December 2021 at the latest.”

This is the time-limit, which Mr Davis had wanted inserted; its omission in the draft had angered the Secretary of State, raising speculation he might quit.

A source close to the Secretary of State explained: "The back-stop paper has been amended and now expresses, in much more detail, the time-limited nature of our proposal; something the PM and David Davis have always been committed to."

However, political opponents seized on the key lines in the document, pointing out how it was not a guaranteed back-stop at all and it referred only to how the UK Government “expects” the preferred customs option to be in place by December 2021; 33 months from the start of Brexit in March 2019.

The Government believes it will never need the back-stop plan - the legal guarantee to maintain frictionless trade between Northern Ireland and the Republic – as it is confident of coming up with its preferred customs option post-Brexit.

Yet UK ministers, after months of deliberation, have still not agreed to their preferred option between the new customs partnership, where the UK would collect border tariffs and pass them onto the EU, and maximum facilitation, using technology to minimise border friction.

The European Commission says both options are unworkable.

No 10 was unable to give any clear indication as to how the internal consideration of the two options was going or whether or not Mrs May and her colleagues were any nearer to choosing one or the other.

At Westminster, Labour’s Chris Leslie was dismissive, saying: "After weeks of the Government negotiating with itself, the fudged document they have produced doesn't engage with any of the key Brexit dilemmas and is highly unlikely to lead to anything but more gridlock in the ongoing talks with the EU."

His party colleague Sir Keir Starmer, the Shadow Brexit Secretary, said Mrs May had "signed up to a flawed proposal, which is inconsistent with her earlier commitments".

He added: “The PM should urgently rethink her decision and back Labour’s call for a new comprehensive customs union and new deal with the single market after Brexit.”

In Brussels, Guy Verhofstadt, the European Parliament's Brexit co-ordinator, was downbeat.

"Difficult to see how UK proposal on customs aspects of IE/NI backstop will deliver a workable solution to avoid a hard border & respect integrity of the SM/CU,” he tweeted, adding: "A backstop that is temporary is not a backstop, unless the definitive arrangement is the same as the backstop."

Michel Barnier, the EU’s chief negotiator, also took to social media to welcome the Government’s back-stop plan but said there were three questions: “Is it a workable solution to avoid a hard border? Does it respect the integrity of the SM/CU? Is it an all-weather backstop?”

Nigel Dodds of the DUP stressed how the back-stop plan “applies to the entire United Kingdom; that is positive and a step forward”.

He added: “It is another demonstration of the Prime Minister's commitment to the Union. The previously proposed annexation of Northern Ireland was totally unacceptable.”