DOWNING Street has insisted that UK ministers are “working together as a team” after Jeremy Hunt told Boris Johnson to “belt up” over Brexit for fear he was helping the Brussels cause in UK-EU talks.

But First Minister Nicola Sturgeon branded the Cabinet row over future customs arrangements an “absurdity,” which strengthened the argument for the UK staying in the single market and customs union.

And her SNP colleague Ian Blackford, who leads the party at Westminster, urged Theresa May to “override her hard Brexit wing – and after two years of endless desperate confusion – make a decision” on the country’s future trading arrangements and back staying in the customs union.

READ MORE: Nicola Sturgeon insists Brexit process has strengthened case for Scottish independence

As senior UK ministers continued to examine in detail the Conservative Government’s two options on future customs arrangements – the customs partnership and maximum facilitation or “max-fax” – tensions once again spilled over in public.

After the Foreign Secretary last week branded Theresa May’s preferred customs partnership option “crazy” and his Cabinet colleague and fellow Brexiteer Michael Gove, the Environment Secretary, said the plan had “flaws,” the Health Secretary urged his colleagues to express their views not in public but behind the Cabinet door.

"I do think that it is important that we have these debates in private. Not just because of collective responsibility, which is what democracy depends on, but also because this is a negotiation. On the EU side, if they see divisions in the open, they will exploit that," declared the UK Government’s Health and Social Care Secretary.

Mr Hunt said Mr Johnson had a very important role to play in the Government and that it “doing what he wants” in terms of Brexit.

"But we have to recognise that we are not the only people who read the papers in Britain and we need to give Theresa May some space. If we are going to have these lively debates, we should have them in private because that will strengthen Theresa May's negotiating hand," explained the Health Secretary.

READ MORE: Nicola Sturgeon insists Brexit process has strengthened case for Scottish independence

Asked if his message to Mr Johnson was to "belt up", Mr Hunt replied: "You could say that. I'd say he is a marvellous foreign secretary but let's work as a team."

Asked if the open Cabinet divisions were hampering the Government’s bid to choose one of the options, No 10 said Mr Hunt had said it was “important the Government worked together as a team on delivering on Brexit and that is what the Government is doing”.

Asked again about the Health Secretary slapping down his Cabinet colleague, the PM’s spokesman insisted the Government was working to “refine” the two Brexit options on future custom arrangements with the EU and “that is what we are focused on”.

Senior ministers met in two groups on Monday to try to iron out problems with the two options before they were due to be discussion on Tuesday at the special Brexit sub-committee, dubbed the War Cabinet.

Sources suggested that a final decision would not be made today but time is beginning to run as Brussels wants to know the UK’s position on future customs arrangement by the time of the European Council in June.

Mrs May spent much of yesterday holding a series of meetings with Tory MPs to discuss the two options. When asked about them and their purpose, her spokesman simply said she met Tory MPs “all the time”.

READ MORE: Nicola Sturgeon insists Brexit process has strengthened case for Scottish independence

One Tory backbencher said there was a slide presentation with Gavin Barwell, the PM's chief of staff, going through the pros and cons of each option.

Meanwhile, Mr Johnson was asked whether or not his differences with Mrs May over post-Brexit customs arrangements were now so deep that he should resign.

He responded by saying he believed the PM's position as set out in an article for the Sunday Times, promising to come out of the customs union to enable frictionless trade with no hard Irish border and enable Britain to make its own trade deals across the globe was "the right one".