Manfred Weber criticised Britain’s apparent desire to still do business with the European Union while not being a member of the bloc.
He also claimed the Foreign Secretary was attempting to “provoke” Brussels with his recent choice of words while speaking in India.
Downing Street was forced to defend Mr Johnson after he compared French President Francois Hollande to someone “who wants to administer punishment beatings to anyone who chooses to escape in the manner of some WW2 movie”.
A No.10 spokesperson said the Foreign Secretary’s “theatrical” comparison “was in no way suggesting that anyone was a Nazi”, pointing to the reaction to Mr Johnson’s choices of words as what Theresa May had criticised as a “hyped-up media report”.
Manfred Weber attacked Boris Johnson, calling him a "clown" for his comments in India
Boris Johnson is acting like a clown and taking away the credibility of the Government
The MEP said Britain was as much of the part of the battle against populist right-wing movements who want to destroy the Union’s “partnership approach” and accused Mr Johnson of following their combative rhetoric.
“Quite frankly, when I hear the words of Boris Johnson that is exactly what I mean,” the German said.
“To provoke each other, to say to each other that we don’t like each other – that is not the way that we should work.
The German was referring to Mr Johnson accusing President Hollande of nazi-style "punishment"
“And, Boris Johnson is acting like a clown and taking away the credibility of the Government in Britain.”
Mr Weber then moved on to mock the Prime Minister’s recent Brexit speech, where she outlined her desire to leave the bloc’s single market while attaining the “greatest possible” access, in a bid to regain control of the UK’s borders.
Speaking on Tuesday, Mrs May said remaining in the single market would “mean not leaving the EU at all”.
“And that is why both sides in the referendum campaign made it clear that a vote to leave the EU would be a vote to leave the single market,” she added.
“So we do not seek membership of the single market. Instead we seek the greatest possible access to it through a new, comprehensive, bold and ambitious free trade agreement.”
However, Mr Weber rebuked her statement, claiming it remains “dangerous to leave the European Union”.
The German added that he had “no problem” with Brexit and is ready for a “fair deal” to be struck between the UK and Brussels.
“We are ready for a fair deal but we have to discuss what fair means,” he said.
“I have learnt a lot about the Brexit vote, like no-one has told the British people what Europe is all about.
Foreign Secretary Boris Johnson's best gaffes
Wed, July 20, 2016
Bumbling Boris Johnson's best gaffes and most controversial quotes.
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UK Foreign Secretary Boris Johnson said it would take him too long to apologise for the 'rich thesaurus' of rude comments and insults
“For example, when we talk about trade, Theresa May made clear statements on trade, so what is EU?
“EU is the single market, that is a free trade zone – the whole ideal of the European Union, that is what the Brits always wanted.
“That was the idea of Europe – now you say you want to leave the European Union but on the other hand, you say I want to have a free trade agreement, which leads to a situation where nothing will change.
“Do you want to leave the single market or you don’t want to leave – that is the question.”