John McDonnell, Labour’s Shadow Chancellor, has pledged to “call out” hard-left news websites if they promote conspiratorial and antisemitic stories.

In a meeting with Adam Langleben, former Labour councillor, at Westminster on Tuesday evening, Mr McDonnell accepted that articles that played down the issue of antisemitism were now commonplace on some websites – most of which claimed to be supportive of Jeremy Corbyn.

Mr Langleben, who is campaigns officer of the Jewish Labour Movement, told the JC he believed the meeting had been a “positive” one.

He added: “John McDonnell seemed to understand the seriousness of the issue and has pledged to call out those websites responsible for a lot of the fake news and conspiratorial antisemitism behind pumped out by the left today.

“I told John that in my view in order to tackle much of the antisemitism that has infected Labour’s grassroots you needed to be tackling these websites.

“I explained how frequently some of these sites slide from legitimate criticism of say Israeli actions in Gaza into antisemitic conspiracies about Israel harvesting organs.”

Mr McDonnell had initially contacted Mr Langleben after he revealed he had been subjected to antisemitic abuse after he appeared on Channel 4 News and suggested that the Labour leadership’s inability to tackle the issue of antisemitism had led to the failure to win Barnet Council in last Thursday’s local election.

“There was an acceptance by John that the issue had cost Labour in Barnet,” said Mr Langleben.

“He said both Jeremy Corbyn and himself would be visiting Barnet in the near future.”

Mr Langleben had specifically named website The Skwawkbox and accused it of “propagating Labour antisemitism.”

He challenged Mr Corbyn and Mr McDonnell to speak out against what he described as “fake news” websites.  

In a message to Mr Langleben, Mr McDonnell tweeted on Saturday: “Adam. Just picked this up, This is appalling. Can you DM me the detail of where this is coming from? Thanks. John.”

Mr Langleben also spoke of his exclusion from Monday’s Labour Party National Executive Committee (NEC) meeting on antisemitism at the party’s headquarters in central London.

He said two weeks ago, after the JLM was initially invited to the meeting, they emailed a reply to Labour’s general secretary Jennie Formby stating he would be attending in person, while the group’s National Secretary, Peter Mason, would be available for the meeting via telephone.

But Mr Langleben was “uninvited” from the meeting on Monday morning and was refused entry after turning at the party’s offices.

In angry messages on Twitter Peter Mason attacked claims reportedly made by a Labour 'source' suggesting Mr Langleben had been invited to Monday's meeting in error.

Mr Mason wrote: "Unfortunately for nameless ‘Labour Party source’ I have the email chain in which I ask for the terms of reference, agenda and invite list, and get told by reply that they wanted JLM to attend specifically to discuss antisemitism awareness training.to then have my JLM colleagues who’ve toured the country delivering the training that *already exists* unceremoniously uninvited hours before the meeting."