Relations between taxi drivers and cyclists threatened to hit a new low today when it emerged that the leader of London’s cabbies had compared some riders to the Islamic terror group responsible for beheading its victims.

Steve McNamara, general secretary of the Licensed Taxi Drivers’ Association, said cyclists who campaigned vociferously for the Mayor’s cycle superhighways were “almost the sort of Isis of London”.

He said the LTDA had been “lambasted by the cycling community” when it first announced that it was considering seeking a judicial review of the cycle superhighway proposals – a position it maintains unless a temporary trial is introduced before any work to make the schemes permanent.

He told LBC radio:

These people, the zealots of the cycling world, are unbelievable. We have had cyber attacks on our websites. They are all over us like a cheap suit on Twitter and social media. We have had physical threats of violence. You name it, we have had it. It’s absolutely unreal. “The loonies out there in the cycling world, they’re almost the sort of Isis of London. Their views and their politics – if you are not with them, and we are with the majority of it, then nothing is too bad for you. These people are unreal.

Andrew Gilligan, the Mayor’s cycling tsar, said: “It’s a remarkable thing to say and illustrates how badly a few people are getting this issue out of proportion.”

This morning Mr McNamara told me that he had probably gone too far but said he had received a series of “death threats” as a result of the LTDA’s stance. Mr McNamara insisted the LTDA backed the principle of the cycle superhighways as a way to improve safety but was extremely concerned at changes to traffic flow at Westminster bridge and around Parliament Square.

He said motorists heading north over Westminster bridge would no longer be able to turn right at Big Ben onto the Embankment. In addition, drivers heading west on the Embankment would not be able to turn right before Big Ben, forcing them round Parliament Square. He said a better route for the superhighway would be along Northumberland Avenue, avoiding any need for it to cut through Parliament Square.

He told me in relation to the Isis remarks: “Perhaps I would accept that was a bit strong. It was a live interview. I have had death threats. They say, ‘I hope people you know die screaming of cancer’. I’m convinced that if 99 per cent of cyclists knew some of the stuff we had received after expresing legitimate concerns, they would be horrified.

“I’m not going to be intimidated. I don’t take them seriously. We have not reported anything to the police because I don’t think there is anything in them. I think it’s just a few loonies, but they really have got a sort of religious zeal.

“Perhaps that was a bit strong [to compare them to Isis] but I can’t think of a single other movement in the world at the moment that behaves in such a vitriolic and aggressive manner.”