Hope Not Hate has threatened to take Nigel Farage to court after the Brexit leader highlighted the Soros-funded group’s extremist leanings in an interview on LBC radio.

Its chief executive Nick Lowles announced on Twitter that he intends to take legal action against Mr. Farage after the former UKIP leader asserted that Hope Not Hate are an extremist group.

The row broke out after Farage said the attack in Berlin was terrible news but “no surprise”, adding: “Events like these will be the Merkel legacy.”

Brendan Cox, husband of murdered Labour MP Jo Cox, replied with a tweet which appeared to accuse the UKIP MEP of extremism.

Speaking on LBC of the spat, Farage said: “Well, of course, he would know more about extremists than me, Mr. Cox. He backs organisations like Hope Not Hate, who masquerade as being lovely and peaceful, but actually pursue violent and undemocratic means.”

On its website, the organisation has placed an appeal asking for money to help fund legal action against the former UKIP leader.

The group says it has “a proud history of campaigning against extremism and hatred”, and claims to have “no idea on what Mr Farage bases his outrageous comments”.

But Farage has on a number of occasions detailed how Hope Not Hate members disrupt his meetings and events, and revealed to the BBC in 2014 that he had to hire bodyguards as a result of the group’s harassment campaign.

In June, masked, left-wing activists who social media users identified as linked to Hope Not Hate, shouted down and physically disrupted the UKIP MEP on a visit to Northampton, forcing him to cancel a planned talk in the town centre.

Hope Not Hate have repeatedly used their resources to attack mainstream conservative groups, moderate and reformist Muslims, and have backed some hard left and “anti-fascist” groups who stand accused of violence and intimidation.

In December last year, in a report on the “Counter-Jihad movement”, the group labelled hijab wearing, practising Muslim Raquel Saraswati, who campaigns against regressive forms of Shariah law, an “anti-Muslim extremist”.

Friends of the campaigner pointed out that the move put Ms. Saraswati’s life at risk, as she could be labelled an “apostate” by the Muslim fundamentalists she works to engage with, as a result of Hope Not Hate’s claims. Her name was later removed from the list.

The same report also targeted Quranic scholars such as Tawfik Hamed, a former extremist turned reformer, which led to former government adviser Maajid Nawaz labelling the document “hate-filled” and a “witch hunt”.

Other editions of the same report have included eminent conservative philosopher Roger Scruton, writer David Horowitz, Canadian journalist Ezra Levant, and Dutch MEP Geert Wilders.

In 2012 the Barnabas Fund, a charity for minority Christians in majority Muslim countries, was labeled “extremist” for its work. The charity was later removed.

The group’s head, Nick Lowles, has himself been branded an extremist by Britain’s National Union of Students (NUS), who recommended he be “No Platformed” on the basis of “Islamophobia”.

A study into claims made by the body about “hate speech” on Twitter following Jo Cox’s murder found that Hope Not Hate exaggerated the volume of it by more than 3,000 per cent.