BORIS Johnson has been told to keep out of public debate over what sort of post Brexit customs arrangement the UK Cabinet wants to have with the EU after he described the Prime Minister’s favoured option as “crazy”.

The Conservative health secretary Jeremy Hunt rebuked Johnson yesterday after the outburst by the Foreign Secretary last week.

In an interview yesterday Hunt warned Johnson his public criticism could undermine the UK’s Brexit negotiating position and said he thought “it’s important that we have these debates in private”.

He told BBC Radio 4’s Today programme: “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.”

Pressed if his message would be “Boris belt up”, Hunt replied to the interviewer: “You could say that – I would say he’s a marvellous foreign secretary but let’s work as a team.”

Remain and Brexiteer members of the Tory Cabinet are at loggerheads over the two options for future customs arrangements.

May and the Remainers want a customs partnership model which would see the UK collect tariffs set by the EU customs union on goods coming into the UK. If those goods didn’t leave the UK and UK tariffs on them were lower, companies could then claim back the difference.

A second “maximum facilitation” or max fac option, favoured by the Brexiteers would rely on using new technologies and things like trusted trader schemes, which could allow companies to pay duties in bulk every few months rather than every time their goods crossed a border.

However, neither option has found favour with the EU which wants the UK to come up with a solution to keep the Irish border open.

Nicola Sturgeon slammed the “absurdity” of the Cabinet split during an address to business leaders in London yesterday saying the row strengthened the case for remaining in the single market. “I deeply regret the UK’s decision to leave the EU and I believe the absurdity – and I believe that is the appropriate word – of the ongoing UK cabinet discussions and disputes over the post-Brexit customs arrangements strengthens one of the basic arguments that the Scottish Government together with many businesses has been making,” she said. “That argument is that in our view the approach if the UK is determined to leave the EU is to remain within the single market and within a customs union. It is ... the obvious democratic compromise in a UK where 48% of voters and indeed two out of the four nations in the UK chose to remain in the EU. It is also the least damaging solution economically.”

Meanwhile, Germany’s foreign minister Michael Roth expressed concern over a lack of progress on the UK side as he joined other EU ministers in Brussels for a meeting with the EU’s chief Brexit negotiator Michel Barnier. “We are concerned there is no clear attitude and no clear position from the British side ... Time is passing.

“We must now make substantial progress, and that is yet to come. What preoccupies us above all is the question of Northern Ireland, where we are still awaiting a substantial approach from the British side.”