Jean-Claude Juncker has accused Boris Johnson of spreading “lies” during the Brexit referendum campaign, in his most strongly worded attack on the prime minister yet.

Speaking on Thursday evening the European Commission president said he “should have intervened” in the campaign to point out “bulls***” and falsehoods spread by “Boris Johnson and others”.

“They were saying things, some of them – lying. Telling the people things which have nothing to do with our day by day reality,” he told an audience at a think tank in Brussels.

“David Cameron asked me not to intervene in the referendum campaign because he said the European Commission is even less popular on the islands than on the continent ... That was a major mistake: I should have intervened, because nobody was denying, contesting the lies Boris Johnson and others were spreading around.”

But the commission president denied that it was the EU’s fault that the campaign had been lost, instead pointing the finger at the British press, in which the prime minister once worked as a Brussels correspondent.

“If for 46 years you are told day after day, and you are reading in your papers, that the place of the British is not really in Europe, but that they are there for economic and internal market reasons, and all the rest – it’s nonsense, bulls***, as they are saying in the European parliament – don’t be surprised if voters are asked to give their impression, some of them, a small majority but nevertheless a clear majority, is voting like a majority of the British sovereign people is voting,” he said.

Mr Juncker is not the first EU leader to lambast Leave campaigners in the strongest terms. In March this year Emmanuel Macron said Brexiteers were “anger-mongers backed by fake news” whose “lies and irresponsibility” had thrown Europe into danger.

Nobody was denying, contesting the lies Boris Johnson and others were spreading around Jean-Claude Juncker, European Commission president

But last week the French president, who had stopped short of naming Mr Johnson in his earlier tirade, claimed he had not been taking about the prime minister, telling journalists at an EU summit: “I never described Boris Johnson” as such.

European Council president Donald Tusk also angered Brexiteers after he said in February that there was a ”special place in hell” for “those who promoted Brexit without even a sketch of a plan” of how to carry it out successfully.

During the same think tank speech, Mr Juncker, who is due to leave office at the end of the month, said: “Brexit could have brought the house down, acted as a catalyst for others, split Europe”. He added: “But it did not. Unity has prevailed. And one should not underestimate how many conversations and encouragements this took me and Michel Barnier. European resilience and strength has shone through.”

Biggest lies told by Boris Johnson Show all 5 1 /5 Biggest lies told by Boris Johnson Biggest lies told by Boris Johnson Made-up quote for The Times Johnson was sacked from The Times newspaper in the late 1980s after he fabricated a quote from his godfather, the historian Colin Lucas, for a front-page article about the discovery of Edward II’s Rose Palace. “The trouble was that somewhere in my copy I managed to attribute to Colin the view that Edward II and Piers Gaveston would have been cavorting together in the Rose Palace,” he claimed. Alas, Gaveston was executed 13 years before the palace was built. “It was very nasty,” Mr Johnson added, before attempting to downplay it as nothing more than a schoolboy blunder. PA Biggest lies told by Boris Johnson Sacked from cabinet over cheating lie Michael Howard gave Boris Johnson two new jobs after becoming leader of the Conservatives in 2003 – party vice-chairman and shadow arts minister. He was sacked from both positions in November 2004 after assuring Mr Howard that tabloid reports of his affair with Spectator columnist Petronella Wyatt were false and an “inverted pyramid of piffle”. When the story was found to be true, he refused to resign. PA Biggest lies told by Boris Johnson Broken promise to boss In 1999 Johnson was offered editorship of The Spectator by owner Conrad Black on the condition that he would not stand as an MP while in the post. In 2001 he stood - and was elected - MP for Henley, though Black did allow him to continue as editor despite calling "ineffably duplicitous" PA Biggest lies told by Boris Johnson Misrepresenting the people of Liverpool As editor of The Spectator, he was forced to apologise for an article in the magazine which blamed drunken Liverpool fans for the 1989 Hillsborough disaster and suggested that the people of the city were wallowing in their victim status. “Anyone, journalist or politician, should say sorry to the people of Liverpool – as I do – for misrepresenting what happened at Hillsborough,” he said. PA Biggest lies told by Boris Johnson ‘I didn’t say anything about Turkey’ Johnson claimed in January, that he did not mention Turkey during the EU referendum campaign. In fact, he co-signed a letter stating that “the only way to avoid having common borders with Turkey is to vote Leave and take back control”. The Vote Leave campaign also produced a poster reading: “Turkey (population 76 million) is joining the EU”

He added that Brexit was “a shame” and would not serve the interests of either the UK or EU.

The president’s comments show the strength of feeling about Brexit that still exists on the continent, with the decision bewildering many of Britain’s allies.