Trade union Unite has threatened social media users that it is seeking “legal advice” in relation to the accusation that its general secretary is “an antisemite and a racist”, which it has called "defamatory".

Last week, David Levene, a Jewish member of the union, sent an e-mail to the union’s member service and executive council, in which he told them he was resigning his membership, “after more than a decade… due to Len McCluskey’s outrageous, sectarian attack on the Jewish community.

“The Labour movement is built on the principles of social justice and equality, and I refuse to be represented at work by an antisemite and a racist.”

Mr Levene’s email was prompted by an article written by Mr McCluskey accusing Jewish communal leaders of “intransigent hostility and an utter refusal to engage in dialogue” regarding Labour antisemitism, and appealing “to the leadership of the Jewish community to abandon their truculent hostility, engage in dialogue and dial down the rhetoric, before the political estrangement between them and the Labour Party becomes entrenched.”

Last year, when asked whether Labour had a problem with antisemitism, the Unite boss said “No, I’ve never recognised that. I believe it was mood music that was created by people who were trying to undermine Jeremy Corbyn.”

The executive council of Unite responded to Mr Levene in an e-mail headed “sent on behalf of Andrew Murray, Chief of Staff.”

It said: “Your e-mail to Len McCluskey has been noted, as has been your insulting an [sic] your libellous remarks.

“Under these circumstances, your resignation, as much as we regret losing any member, may be understandable.”

When the correspondence between Mr Levene and Unite was published on Twitter, the union’s social media account began contacting people saying: “Please be aware that legal advice is now being sought on this implied accusation against the chief of staff of our union.”

In response, a number of lawyers indicated that they would be very happy to advise Mr Levene on the issue pro bono.

In response to one Twitter user who said “My guess is that a lot of lawyers - solicitors & barristers - would take the case for the defendants on a no fee basis”, solicitor Stephen Gilchrist responded saying: “no fee? I’d pay the client!”

Another Twitter user commented: ““The due diligence on document discovery will be epic. Unite will have to hand over every single thing McCluskey has ever affixed his name to. Every official publication. Everything he has ever received. Talk about opening Pandora’s Box.”

A Unite spokesman said: “We view the accusations levelled against Unite’s general secretary Len McCluskey as defamatory.  Mr McCluskey is a life-long campaigner against all racism, including against anti-semitism, which is why matters are now subject to consideration by our lawyers.”