THERESA May is coming under pressure to sack Boris Johnson after a Cabinet colleague described the Foreign Secretary as a “clown”, and a top German diplomat, frustrated by the UK’s chaotic approach to Brexit, described the floppy-haired Tory’s approach to diplomacy as “not very clever”.

Newspaper reports yesterday suggested that even the dysfunctional Trump administration found it frustrating having to deal with Johnson.

As May flew into Japan, Downing Street was forced to say the Prime Minister had “full confidence” in the Eton-educated Brexiteer. An unnamed minister had told The Times how poorly people in other countries thought of Johnson: “It’s worse in Europe. There is not a single foreign minister there who takes him seriously. They think he’s a clown who can never resist a gag.”

Other unnamed diplomatic sources told the paper White House officials “don’t want to go anywhere near Boris because they think he’s a joke”.

A spokeswoman for No 10 said: “The Prime Minister meets the Foreign Secretary regularly and they have a good relationship.”

Asked if the Prime Minister had full confidence in Johnson and thought he was doing a good job, the spokeswoman simply stated: “Yes.” Pressed on whether she believed he had the confidence of his European counterparts, the spokeswoman said: “The Prime Minister has a good relationship with Boris Johnson, has full confidence in him and and he’s doing a good job.”

Michael Fuchs, an ally of German Chancellor Angela Merkel, was a little kinder, suggesting Johnson had calmed down in recent weeks.

Fuchs, the deputy parliamentary leader of Merkel’s CDU Party, told BBC Radio 4’s World at One: “It was not very clever from him, the way he handled Europe or European negotiators at the beginning, but I have a feeling that in the last couple of weeks he was rather calm, we didn’t hear much from him so maybe he thought it over and he has to come back to the negotiating table, because it’s a very difficult process and big words don’t help.”

Meanwhile, European Commission President Jean-Claude Juncker said the UK Government’s official papers were not satisfactory and that an “enormous amount” of work needed to be done before there could in any way be talks on a future trade deal.

Britain and the EU are on the third round of Brexit talks this week.

Sources close to Tory Brexit Minister David Davis have insisted an early deal is possible, and that the issue of the the UK’s debts to Europe, the rights of EU citizens in the UK, and the Irish border are all tied up with trade.

Juncker said the UK “hesitates showing all its cards”, but added: “I did read, with the requisite attention, all the papers produced by Her Majesty’s Government and none of those is actually satisfactory. So there is still an enormous amount of issues which remain to be settled.

“Not just on the border problems regarding Ireland and Northern Ireland, which is a very serious problem in respect of which we have had no definitive response, but we also have the status of European citizens living in the UK and UK citizens living on the Continent.

“We need to be crystal clear that we will commence no negotiations on the new relationship – particularly a new economic and trade relationship – between the UK and the EU before all these questions are resolved.”

Downing Street defended the UK’s approach to the talks.

“We believe we are in a good position and would like to move on to discuss our future relationship,” a No 10 spokeswoman said.

“Let’s see what David Davis has to say on Thursday,” she added.

Scotland’s financial sector seemingly has little confidence in what Davis will say tomorrow, with firms reportedly drawing up restructuring “contingency plans” to deal with the impact of a Brexit shock.

Scottish Financial Enterprise, which represents giants such as Royal Bank of Scotland and Scottish Widows, has told MSPs, their members needed to consider the prospect of separate EU bases for firms.

They have said there needs to be “certainty” by the end of this year on the kind of transitional arrangements which will operate between the UK and EU.

But, they have said, many of the leading finance companies are looking at moving some of their operations to other parts of Europe.

Edinburgh is the biggest financial centre in the UK outside London, and the sector accounts for 86,000 jobs and is worth £8.6bn.