Jeremy Corbyn is seeking legal advice after Zarah Sultana sent an “unauthorised email” from Your Party’s account inviting its supporters to become paid-up members.
As the left-wing MP accused Your Party of being run as a “sexist boys’ club”, Mr Corbyn called on his backers to ignore Ms Sultana’s email.
In a statement signed off by the party’s five male MPs, ignoring Ms Sultana, he said anyone who signed up should immediately cancel direct debits and that “legal advice is being taken”.
Responding, Ms Sultana said she had been sidelined by the party she co-founded and that she has “been subjected to what can only be described as a sexist boys’ club”.
She confirmed she had unilaterally taken the decision to send out the membership email to “safeguard the grassroots involvement” that she believes is essential to the party’s success.
The move would allow the left-wing challenger party to start taking paid-up members, as opposed to those who have simply indicated their support via email.
It attracted £20,000 paid members within hours, she said, which could mean income of more than £1m per year.
Former Labour leader Mr Corbyn is seeking legal advice after the message was sent to Your Party’s supporter list.
In a statement, Ms Sultana said: “After being sidelined by the MPs named in today’s statement and effectively frozen out of the official accounts, I took the step of launching a membership portal so that supporters could continue to engage and organise.
“This was in line with the roadmap set out to members … my sole motivation has been to safeguard the grassroots involvement that is essential to building this party.
“Unfortunately, I have been subjected to what can only be described as a sexist boys’ club: I have been treated appallingly and excluded completely.
“They have refused to allow any other women with voting rights on the working group, blocking the gender-balanced committee that both Jeremy and I signed up to.”
Writing on X (Twitter), Mr Corbyn said: “This morning, an unauthorised email was sent to all Your Party supporters with details of a supposed membership portal hosted in a new domain name.
“Legal advice is being taken. That email should be ignored by all supporters.”
Mr Corbyn urged anyone who had signed up to cancel any direct debits.
“Soon, you will be able to turn your support into membership and shape the future of our party and our country,” Mr Corbyn added.
It is the latest chapter in a public spat between the co-leaders which began when the new venture was originally announced by Ms Sultana, who said in July she was quitting the Labour Party to co-found the new venture with Mr Corbyn.
But Mr Corbyn appeared unready for the announcement, making no public statement on the launch until the next day.
Their relationship further broke down after she accused him of “capitulating” over antisemitism when he was Labour leader.
The Islington MP said it was “not really necessary” for Ms Sultana, with whom he is currently co-leading the as-yet-unnamed party, to “bring all that up”.
It came after Ms Sultana used an interview with the New Left Review to say Mr Corbyn as Labour leader “capitulated to the IHRA definition of antisemitism”.
The Coventry MP also said Mr Corbyn alienated voters by “triangulating” on Brexit and that Labour under his leadership was “frightened and far too conciliatory”.
Mr Corbyn said on Tuesday his new party will hold a founding conference in November, with delegates chosen by lottery.
In an email, Your Party said membership applications would open by the end of September.
But it did not give precise dates for the conference, saying only that it would see “thousands” of delegates “chosen by lottery to ensure a fair balance of gender, region and background”.
Ahead of that conference, the party said it would hold “regional assemblies” where members can “listen to each other, break bread and debate” founding documents.
And Thursday’s email took supporters to a page where they could choose a £5 monthly subscription or opt for a £55 annual payment. “This is your chance to help build something new. A party that belongs to its members, not the establishment,” it said.
