UK broadcaster Channel 4 News accused former UK foreign secretary Boris Johnson of lying in his resignation letter yesterday. It used the forthright language in the headline of a piece that saw Boris Johnson fact-checked on his resignation letter as foreign secretary.

In it, he said: “If a country cannot pass a law to save the lives of female cyclists — when that proposal is supported at every level of UK Government — then I don’t see how that country can truly be called independent.”

Channel 4 News found this statement to be the opposite of the truth.

It said: “It’s true that when he was Mayor of London, Mr Johnson campaigned to introduce tougher rules on lorry safety to protect cyclists. But he’s left out some key details.

“For one thing, he neglects to mention that the regulations he’s talking about were in fact put forward by the European Parliament, and backed by 570 MEPs, with 88 voting against. He also fails to acknowledge that those laws have actually been passed.

“More crucially, Mr Johnson is wrong to say that the laws in question were “supported at every level of UK Government. When the regulations were put forward by the EU, the UK Government explicitly did not support the proposals.”

This is not the first time that Johnson has kept the fact checkers busy. Here we look at some of the most notable claims that saw Boris Johnson fact-checked during his political career to date.

Boris Johnson fact-checked: the highlights

Johnson wrote in the Daily Telegraph in September 2017: “And yes – once we have settled our accounts, we will take back control of roughly £350m per week. It would be a fine thing, as many of us have pointed out, if a lot of that money went on the NHS.”

The verdict on this from independent fact-checking charity Full Fact: “This is wrong, it’s more like £250m a week. In any case the impact on the economy from changes to trade after leaving the EU is likely to be far bigger than savings from the UK’s membership fee.”

Pro-Remain website In Facts has a whole page devoted to Johnson’s apparent errors when it comes to statements on the EU.

UK news website iNews also resorted to what would be described in the UK House of Commons as unparliamentary language with a piece headlined: “All the times Boris Johnson flat-out lied”.

It notes that among the “euromyths” peddled by Johnson is the claim he repeated in May 2016 that the EU was setting rules on the shape of bananas. This is something the EU itself dismissed on its Euromyths page as far back as 1994.

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In 2004, Johnson was sacked as shadow arts ministers for the Conservatives after lying about allegations that he had been involved in an extra-marital affair. He described the claims as “an inverted pyramid of piffle” only for them later to be proved true.

For legal reasons, it is unusual for a UK news organisation to accuse politicians of lying. This implies dishonesty, rather than making a mistake, and could be grounds for libel.

But it appears that when it comes to Johnson, given his form, journalists believe that they are on safe ground to do so.