Labour Against The Witchhunt (LAW) - which was launched to defend Labour activists accused of antisemitism - has been rocked by a bitter rift over one of its member’s open support for a Holocaust denier.

Tony Greenstein, LAW’s vice-chair, who was himself expelled from Labour over his use of the word "Zio" and for mocking the phrase Final Solution, has clashed with another of the group’s supporters .

Peter Gregson – who has been backed by LAW since being expelled by the GMB union over alleged antisemitism - had urged Mr Greenstein and his allies to support a petition he started, which included links to an article by Ian Fantom of the conspiracy theory Keep Talking group.

In that article, Mr Fathom writes approvingly of Dr Nick Kollerstrom – author of The Auschwitz ‘Gas Chamber’ Illusion.

But in emails sent to LAW’s leading members – including expelled Labour activist Jackie Walker, her partner Graham Bash and Tina Werkman – Mr Greenstein initially attempts to persuade Mr Gregson to “cut links” with the Mr Fanthom and Mr Kollerstrom, saying the association “would be incredibly damaging” for LAW.

He writes: “I must ask you to remove all references to Ian Fantom’s article from your petition update which directs people to Kollerstrom’s holocaust denial article on the website of the well-known Holocaust denial site CODOH.”

In his March 22 email, Mr Greenstein also refers to wording in Mr Gregson’s petition saying: "It is bad enough that you yourself used the word ‘exaggerate’ in terms of the Holocaust.”

He then adds: "We could put this down to simply using the wrong word.”

But Mr Greenstein’s words spark a furious response from Mr Gregson, despite the fact that the LAW vice-chair spoke in Mr Gregson's defence a hearing into his conduct held by GMB in January.

He writes on March 23 that Mr Greenstein is “exhibiting the kind of shrill neurosis for which the left is rightly famed. And is why of course so many in the left are doomed to obscurity, for they slam the door hard shut at every opportunity."

Mr Fantom has previously shared conspiracy theories blaming Israel for 9/11. But Mr Gregson writes of him: “I have spent time with Ian Fantom. I believe he is OK. I do not have a problem with his politics.”

In his own furious response, Mr Greenstein writes back at 2.54 am, setting out detailed evidence of Mr Fantom's support for Mr Kollerstrom, noting that the article Mr Gregson links to says Mr Kollertrom "had been targeted in a witch-hunt".

"You can call me whatever you want but I am not going to have holocaust denial being debated or legitimised under the guise of ‘free speech’," Mr Greenstein writes.

"It’s like debating the rights and wrongs of murdering 50 Muslims in New Zealand last week, or perhaps that too didn’t happen?

“I am removing you from the LAW Facebook and will leave it to the LAW Steering Committee as to whether you are removed from LAW membership too.”

In a further message on April 3 - still copying in much of the LAW leadership - Mr Gregson writes: "Tony is stating he will seek to damage my reputation by making LAW shun me if I do not do as he asks. If that is not a threat, then I’m a chinaman.”

But Mr Greenstein replies later the same day: "I should not have needed to ask Peter not to associate with holocaust deniers and conspiracy cranks.  That was self-evident or should have been.

“Nor did I threaten him and I merely made it clear that we could not work with him whilst he kept company with such ‘friends’.

“Yes there is freedom of speech to deny the holocaust but my freedom of speech includes keeping a wide berth from Peter.”

Two days later, Jackie Walker, now clearly fed up with the conflict, writes: "Tony, Peter – if you want to continue this please use your own emails.”

But Mr Greenstein, responding to Ms Walker and everyone else in the email chain, writes: "Sorry I don’t know what type of a group this is. 

"I haven’t spammed any one. I have simply replied to Peter Gregson’s unsolicited emails. I won’t do so anymore and as far as I am concerned the group is at an end. So no need for anyone to withdraw as there is nothing to withdraw from.”

Mr Gregson then explains his decision to place the entire email chain on his web site, writing: "Nick Kollerstrom never denies the Nazis murdered many, many Jews.

“He just thinks it was by shootings and hangings, not gassing. I don’t think one can call him a Holocaust denier; he does not deny that the Nazis were out to destroy the Jewish race. In this respect he might be described as a Holocaust sceptic. He himself says he is not a denier.

“He has a 1.5 minute video where he says he accepts the mass murder of Jews in WW2. I believe he is a historical revisionist. I believe his research is toxic and not something I agree with.

“But I still believe in his right to say these things. Same as I believe that Hodge has a right to call Jezza an anti-Semite.

“I also think she should have been disciplined by Labour for so doing, for bringing the Party into disrepute. I am, quite simply, a believer in free speech.

“Because Tony has banned me from the Labour Against the Witch-hunt (unofficial) Facebook page and is now publicly accusing me of consorting with Holocaust deniers, I feel it is necessary to make all correspondence on this matter public.”