Labour has given the co-chair of the pro-Jeremy Corbyn Jewish Voice For Labour group a written warning about her conduct - days before she appears at an event with Shadow Chancellor John McDonnell.
Jenny Manson was rebuked over her comments she made at a Finchley and Golders Green Constituency Labour Party meeting in July, where she compared Section 28 legislation, which prohibited the promotion of homosexuality in schools, to the IHRA definition of antisemitism.
The letter sent by Labour's complaints team to Ms Manson reminds her of the conduct expected of members and warns that any repeat of such behaviour might result in disciplinary action.
The JC revealed shortly after the meeting that LGBT members of the local party were writing to complain.
Local Labour member Luisa Attfield tweeted: "As a Jewish lesbian I am offended and as person with a brain its a baseless comparison."
On Twitter, JVL tried to calm the row, saying Ms Manson had "compared the chilling effects on free speech of thought of S28 and the IHRA".
But local Cllr Arjun Mittra responded: "This is a lie. I was in the room. She compared IHRA to section 28. You are back-pedalling because you know the mask has slipped."
On Twitter, Ms Attfield was called a "lying lesbian" and Cllr Mittra was called an "uncle Tom" by Tony Greenstein, a former Labour member who has used antisemitic slurs such as "Zio" and was expelled from the party earlier this year, but who spoke at JVL's event at Labour conference in Liverpool last month.
Mr Greenstein is also among those to have contributed towards a crowdfunding campaign supporting Ms Manson's bid to be an MP.
A gofundme.com page launched to 'Make Jenny Manson A Labour MP' includes a donation from Mr Greenstein and one from Fred Leplat - who was expelled from the Labour Party earlier this year over membership of a separate far-left organisation.
The JC has learned that several previous supporters of Ms Manson in the Finchley and Golders Green Labour Party have decided to back another pro-Corbyn candidate over fears that the JVL activist's reputation is now "too toxic."
One local member told the JC: "Jenny Manson's record of past mistakes is as long as my arm. Her opponents would have a field day if we picked her as Labour's candidate. There's far better options available than her."
When asked about her written warning, Ms Manson said: "There are no disciplinary procedures against me. It is a breach of data protection to leak information about any confidential correspondence between the party and its members."
