Anti-fascist campaign group Hope Not Hate has launched a crowd-funding campaign to sue Nigel Farage after he referred to them as “extremists” who “masquerade as being lovely and peaceful but actually pursue violent and very undemocratic means”.

The organisation’s director, Nick Lowles, announced on Twitter it had written to the former Ukip leader demanding he withdraw the claims or face legal action.

Mr Farage made the comments during a scathing attack on Brendan Cox, the husband of murdered Labour MP Jo Cox.

The row came after Mr Cox criticised the Ukip MEP for blaming German Chancellor Angela Merkel for a terrorist attack on a Christmas market in Berlin.

Hope Not Hate has now launched a public fundraising website to cover the costs of taking Mr Farage to court.

It said: “Nigel Farage's allegations against Hope not hate on LBC today are a political smear, which is why our lawyers have written to Mr Farage demanding that he retracts and publicly apologises for his remarks, or face further legal action.

“Hope not hate is a well-respected, civil society organisation whose more than 200,000 supporters come from all political persuasions. They are united by a common desire to combat racism and to do so using lawful, peaceful means.

“That Nigel Farage made his remarks in the context of a discussion about Jo Cox, who was so brutally murdered earlier this year, makes them all the more poisonous and hateful.

"As is well known, Hope not hate was one of three entities chosen by Jo’s widow, Brendan Cox, as the recipient of donations from the public who wished to show their solidarity with the family.”

Nigel Farage's most controversial moments Show all 12 1 /12 Nigel Farage's most controversial moments Nigel Farage's most controversial moments When he unveiled that 'breaking point' poster during the referendum Mr Farage was accused of deploying “Nazi-style propaganda” when he unveiled a poster showing Syrian refugees travelling to Europe under the next “Breaking point”. Users on social media were quick to compare the advert to a Nazi propaganda film with similar visuals and featuring Jewish refugees. The poster was particularly controversial because it was unveiled the morning of the killing of Labour MP Jo Cox Rex Nigel Farage's most controversial moments When he said he’d be concerned if his neighbours were Romanian In May 2014 Mr Farage was accused of a “racial slur” against Romanians after he suggested he would be concerned living next to a house of them. “I was asked if a group of Romanian men moved in next to you, would you be concerned? And if you lived in London, I think you would be,” he told LBC radio during an interview. Asked whether he would also object to living next to German children, he said: “You know the difference” Bongarts/Getty Images Nigel Farage's most controversial moments When he said the EU campaign was won 'without a bullet being fired' Nigel Farage has said the next Prime Minister has to be a Leave supporter AFP/Getty Nigel Farage's most controversial moments When he resigned as Ukip leader and came back days later After failing to win the seat of South Thanet at the general election, Nigel Farage stepped down as Ukip leader – as he had promised to do during the campaign. Days later on 11 May he “un-resigned” and said he would stay after being convinced by supporters within the party. We’ll see how long his resignation lasts this time AP/Matt Dunham Nigel Farage's most controversial moments When he blamed immigrants for making him late Mr Farage turned up late to a £25-a-head ‘meet the leader’ style event in Port Talbot, Wales in December 2014. Asked why he was late, he blamed immigrants. “It took me six hours and 15 minutes to get here - it should have taken three-and-a-half to four,” he said. “That has nothing to do with professionalism, what it does have to do with is a country in which the population is going through the roof chiefly because of open-door immigration and the fact that the M4 is not as navigable as it used to be” Getty Nigel Farage's most controversial moments When he wanted to ban immigrants with HIV from Britain Mr Farage has used his platform as Ukip leader call for people with HIV to be banned from coming to Britain. Asked in an interview with Newsweek Europe in October 2014 who he thought should be allowed to come to the UK, he said: “People who do not have HIV, to be frank. That’s a good start. And people with a skill.” He also repeated similar comments in the 2015 general election leadership debates Getty Nigel Farage's most controversial moments When he defended the use of a racial slur against Chinese people Defending one of Ukip’s candidates, who used the word “ch**ky” to describe a Chinese person, Mr Farage said: “If you and your mates were going out for a Chinese, what do you say you're going for?" When he was told by the presented that he “honestly would not” use the slur, Mr Farage replied: “A lot would” Lintao Zhang/Getty Images Nigel Farage's most controversial moments When he said parts of Britain were ‘like a foreign land’ The Ukip leader used his 2014 conference speech to declare parts of Britain as being “like a foreign land”. He told his audience in Torquay that parts of the country were “unrecognisable” because of the number of foreigners there. Mr Farage has also previously said he felt uncomfortable when people spoke other language on a train Screengrab Nigel Farage's most controversial moments When he said the British army should be deployed to France At the height of trouble at Britain’s Calais border Mr Farage proposed a novel solution. The Ukip leader called for the British army to be sent to France to put down a migrant rebellion. “In all civil emergencies like this we have an army, we have a bit of a Territorial Army as well and we have a very, very overburdened police force and border agency,” he said. “If in a crisis to make sure we’ve actually got the manpower to check lorries coming in, to stop people illegally coming to Britain, if in those circumstances we can use the army or other forces then why not” AFP/Getty Nigel Farage's most controversial moments When he said breastfeeding women should ‘sit in the corner’ Mr Farage sparked protests from mothers after he told women to “sit on the corner” if they wanted to breastfeed their children. “I think that given that some people feel very embarrassed by it, it isn’t too difficult to breastfeed a baby in a way that's not openly ostentatious,” Mr Farage said. He added: "Or perhaps sit in the corner, or whatever it might be” AFP/Getty Images Nigel Farage's most controversial moments When he said the gender pay gap exists because women are ‘worth less’ At a Q&A on the European Union in January 2014 Mr Farage said there was no discrimination against women causing the gender pay gap. Instead, he said, women were paid less because they were simply “worth far less” than many of their male counterparts. “A woman who has a client base, has a child and takes two or three years off - she is worth far less to her employer when she comes back than when she went away because that client base won't be stuck as rigidly to her portfolio,” he said Getty Nigel Farage's most controversial moments When he said he actually couldn’t guarantee £350m to the NHS after Brexit During the EU referendum campaign the Leave side pledged to spend £350 million a week on the National Health Service – claiming that this is what the UK sends to Brussels. Nigel Farage didn’t speak out against this figure and also pledged to spend EU cash on the health service and other public services himself. Then the day of the election result he suddenly changed his tone, saying he couldn’t guarantee the cash for the NHS and that to pledge to do so was “a mistake” Getty

A source close to Mr Farage told The Independent: “It’s quite funny, in an ironic way, that an organisation in receipt of a huge sum of money from the Jo Cox Fund is now crowd-sourcing an attempted legal action.

On the issue of Mr Cox’s comments, the source said: “There are many ways to jump on a bandwagon.

"Brendan Cox and his children have suffered a great deal this year, but equally there are people in Germany suffering right now.”

The row began after Mr Farage tweeted: “Terrible news from Berlin but no surprise. Events like these will be the Merkel legacy.”

Mr Cox, whose wife was shot dead by right-wing extremist Thomas Mair shortly before the EU referendum, responded by saying: “Blaming politicians for the actions of extremists? That's a slippery slope Nigel."

Mr Farage then uses a radio interview to launch an attack on Mr Cox.

He told LBC: “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 very undemocratic means.”