Number 10 has insisted Boris Johnson was just making a "theatrical comparison" when he likened the French President to a World War Two guard.
The Foreign Secretary had warned Francois Hollande not to hit the UK with World War Two-style "punishment beatings" for leaving the EU.
His comments were condemned as "crass", "abhorrent" and "wild and inappropriate", but a spokeswoman for Theresa May insisted he had not been comparing the French President to a Nazi.
Mr Johnson had been responding to comments that Mr Hollande would not be prepared to give the UK a better deal outside the single market than it had in it.
He said: "If Monsieur Hollande wants to administer punishment beatings to anybody who chooses to escape, rather in the manner of some World War 2 movie, then I don't think that that is the way forward and I don't think it's in the interests of our friends and partners."
A senior Labour spokesman said: "We are all aware that the Foreign Secretary has a habit of making wild and inappropriate comments.
"Talking about World War Two in that context is another one of those and that is not going to be something that is going to improve the climate for this negotiation."
The Liberal Democrat leader Tim Farron said the remarks were an "utterly crass and clueless remark from the man who is supposed to be our chief diplomat".
European Parliament Brexit negotiator Guy Verhofstadt tweeted: "Yet more abhorrent & deeply unhelpful comments from Boris Johnson which PM May should condemn."
But a spokeswoman for Mrs May condemned the reports of Mr Johnson's comments as "hyped up".
She added: "There is not a Government policy of not mentioning the war."
During the EU referendum campaign, Mr Johnson came under fire for comparing the aims of the EU to those of Adolf Hitler.
Mr Johnson made his comments after the Prime Minister warned EU leaders in her key Brexit speech that offering a bad deal to punish the UK for its decision to leave the EU would be "an act of calamitous self-harm".
Mrs May said if the UK was offered a bad exit deal she would be prepared to move to a low-tax economy to make the country a more attractive place to do business than the EU.
EU Commission President Jean-Claude Juncker said on Wednesday that while the negotiations would be "very, very difficult" EU leaders were "not hostile" to the UK.
He said he had spoken to Mrs May after her speech on Tuesday.
Mr Juncker said: "We want a fair deal with Britain and a fair deal for Britain, but a fair deal means a fair deal for the European Union too."
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Source : https://uk.news.yahoo.com/no-10-boris-johnson-did-161400449.html