Boris Johnson's sister launches extraordinary attack on his 'reprehensible' Jo Cox comments as his allies warn of violence if Brexit is not delivered

• Boris Johnson's sister launches an extraordinary attack on his "deeply reprehensible" language after he was accused of inciting violence and hatred against Members of Parliament
• Rachel Johnson claimed her brother was wrong to say the best way to honour the memory of murdered MP Jo Cox, who campaigned against leaving the EU, was to deliver Brexit.
• She said: "It was a very tasteless way of referring to the memory of a murdered MP - murdered by somebody who said "Britain First" - who is obviously of the far-right tendency which you could argue is being whipped up by this sort of language."
• Her comments come as a Cabinet minister told the Times on Friday that the country risked a "violent, popular uprising" if a second referendum result overturned the original vote to leave the EU.
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Boris Johnson's sister has launched an extraordinary attack on his "deeply reprehensible" language, which she said was whipping up far-right hatred of the kind that led to the murder of Labour MP Jo Cox in 2016.

The attack on the prime minister's behaviour came after senior allies warned that Britain would face civil unrest on the scale of the gilets jaunes protests in France or the Los Angeles riots if Brexit was not delivered.

Rachel Johnson - a prominent journalist who is a vocal critic of her brother's Brexit position - said her brother was wrong to suggest that the best way to honour the memory of Jo Cox, who campaigned for Remain, was to take the UK out of the EU.

"It was particularly tasteless for those who are grieving a mother, an MP, and a friend to say that the best way to honour her memory is to deliver the thing that she and her family campaigned against, which is Brexit," Johnson told Sky News.

"It was a very tasteless way of referring to the memory of a murdered MP - murdered by somebody who said "Britain First" - who is obviously of the far-right tendency which you could argue is being whipped up by this sort of language."

The comments come after Johnson's brother earlier this month resigned from his government in protest at his Brexit policy.

Read more: Boris Johnson's own brother dramatically quit as an MP and government minister, accusing him of trashing the national interest

Watch Boris Johnson's sister speak out against him

The prime minister faced a furious backlash on Thursday after he dismissed as "humbug" a warning from one Labour MP that his "inflammatory" rhetoric was contributing to violent threats against MPs.

He said that "tempers need to come down" and said he would need to "reach out" to opposition MPs to secure support for a deal.

But he refused to apologise for describing attempts to delay a no-deal Brexit as a "surrender act," despite warnings from Labour MPs that such language is being incorporated into death threats against them and their families.

Rachel Johnson said: "My brother is using words like 'surrender' and 'capitulation' as if the people standing in the way of the blessed will of the people, as defined by the 17.4 million votes in 2016, should be hung, drawn, quartered, tarred, and feathered.

"I think that is highly reprehensible."

But despite the prime minister calling for calm, an unnamed Cabinet minister told the Timeson Friday that the country risked a "violent, popular uprising" if a second referendum result overturned the original vote to leave the EU.

They added: "In this country we never had the gilets jaunes or the LA riots [in 1992]. People just don't think it's possible in this country because it has not happened before. Now they have a model - gilets jaunes - they have encrypted phones to co-ordinate it, and it only takes a couple of nasty populist frontmen to inspire people."

Dominic Cummings, the prime minister's chief adviser, further inflamed tensions when he said: "We are enjoying this, we are going to leave and we are going to win."