Boris Johnson’s weekend intervention in Brexit negotiations has been received with open-mouthed disbelief across continental European newspapers.

Most outlets suggested the Foreign Secretary’s 4,000-word Daily Telegraph article spelling out his own Brexit plan would weaken Theresa May’s hand with EU negotiators still further – just days ahead of her crunch speech in Florence.

“The EU will follow the civil war within the Tories with horror,” analysis from Germany’s pro-business Handelsblatt newspaper summarised.

“For nothing makes negotiations more difficult than an unpredictable partner who does not know what he wants.”

French daily newspaper Le Monde described the Foreign Secretary’s intervention as having “a nationalist tone” and warned that it “risks reviving the war on Europe within the Tories and weakening the already difficult position of the Prime Minister, not only on the domestic level, but in the negotiations with the EU-27”.

The issue of Mr Johnson’s false claim that £350 million would be available for UK public spending once Britain had left the bloc was treated with rather less benefit of the doubt in the continental press than in British outlets.

While the BBC has been under fire on social media for claiming that Mr Johnson’s false claim that the UK sends £350 million to the EU every week is merely “disputed”, Spanish newspaper El Pais simply said the minister had resurrected a “proven lie” from the referendum campaign.

The daily paper’s analysis adds that the Prime Minister’s failure to sack the Foreign Secretary for such an overt leadership bid adds “further evidence of her weakness just when the country needs someone strong”.

Theresa May has ‘full confidence’ in the Foreign Secretary, Downing Street said (Chris J Ratcliffe/AFP)

Downing Street on Monday flat-out refused to acknowledge that Mr Johnson had deviated from the Government line on Brexit, with a spokesperson saying the PM had “full confidence” in the minister. The spokesperson, however, conceded that Mr Johnson's article published online on Friday night had not been cleared by Number 10.

Mr Johnson has been given a back-seat role in Brexit negotiations despite his post as Foreign Secretary, with day-to-day negotiations delegated to Davis Davis, the Brexit Secretary.

Brexit: the deciders Show all 8 1 /8 Brexit: the deciders Brexit: the deciders European Union's chief Brexit negotiator, Michel Barnier Getty Brexit: the deciders French President Emmanuel Macron Getty Brexit: the deciders German Chancellor Angela Merkel Reuters Brexit: the deciders Commission President Jean-Claude Juncker EPA Brexit: the deciders The European Parliament's chief Brexit negotiator Guy Verhofstadt Getty Brexit: the deciders Britain's Prime Minister Theresa May Getty Images Brexit: the deciders Britain's Chancellor of the Exchequer, Philip Hammond PA Brexit: the deciders After the first and second appointed Brexit secretaries resigned (David Davis and Dominic Raab respectively), Stephen Barclay is currently heading up the position PA

Liam Fox, the International Trade Secretary, has been tasked with negotiating trade deals outside the EU – leaving the Foreign Secretary with the other, more limited, aspects of foreign policy.