An extraordinary split has opened between Jeremy Corbyn and Zarah Sultana in the formation of their new leftwing party, with the former Labour leader confirming a referral to the Information Commissioner’s Office over an unauthorised membership portal promoted by his co-leader.Corbyn said the site had been set up without approval, describing it as a “false membership system” that collected money and data without authorisation.He confirmed the party had referred the matter to the ICO and urged supporters to ignore an earlier email requesting funds and cancel any payments.Responding to claims from Sultana that she had been frozen out by a “sexist boys’ club” inside the party, Corbyn said late on Thursday that she had not been “excluded from any discussions” and remained part of a process “rooted in inclusivity and mutual respect”.Sultana rejected those claims, saying she acted because she was sidelined and frozen out of official accounts.

She said her only aim was to “safeguard grassroots involvement”, as she accused Corbyn’s allies of trying to concentrate power over members’ money and the party’s conference.Allies of Sultana went further, suggesting a “paranoid anti-democratic faction” inside the project worked to exclude her from decision-making and was more concerned about preserving its own status than building the movement.They claimed this group had been developing a rival membership system that would divert money to its own company, giving it “complete control” over the party.Sultana’s allies claim there had been an internal agreement that one faction would hold mailing list data, while a different more pro-democratic group controlled donor information, in an attempt to split power.They allege she had exhausted every avenue to resolve the dispute privately before being “stonewalled”.

The split emerged on Thursday when Sultana revealed a new membership portal on X, urging supporters to “be a part of history”.Within half an hour she celebrated “10,000 paid-up members” in a separate post and reassured her followers that the membership site was “safe and secure”, encouraging them to keep trying to sign up despite “issues due to such high traffic”.By early afternoon, Sultana said numbers had hit 20,000, dismissing suggestions from those she classed as “rightwing bad faith actors” who were claiming “this link is fake”.Sultana had posted about the new portal three times before Corbyn issued an “urgent message” telling his followers on X to ignore the site and indicated “legal advice is being taken”.“This morning, an unauthorised email was sent to all yourparty.

uk supporters with details of a supposed membership portal hosted in a new domain name,” Corbyn said,“Legal advice is being taken,That email should be ignored by all supporters,If direct debits have been set up, they should immediately be cancelled,”The clash is the most dramatic in a series of tensions that have plagued the project since its staggered launch in July.

Sultana, 31, who had been suspended from Labour since a rebellion over the two-child benefit cap, announced unilaterally she was co-leader of a new party along with Corbyn, 76.But some within the group felt the move was premature and potentially counterproductive, while others disagreed – saying the alliance would have never been launched if Corbyn was allowed to remain indecisive.Several hours later, the former Labour leader confirmed he was in discussions about creating the new party but avoided confirming any formal structure or leadership arrangement, giving his preference for collective decision-making.By late July the pair had formally agreed to launch a party together, with a pledge to hold mass gatherings and a founding conference in the autumn.Sign up to First EditionOur morning email breaks down the key stories of the day, telling you what’s happening and why it mattersafter newsletter promotionBut divisions over control and process have resurfaced.

Insiders disagreed over whether the party should operate as a member-driven organisation – with a space for grassroots debate and policy setting – or take on a tighter model built around a small group of MPs and organisers.There have also been divisions over control of membership data and finances.It was those that burst into the open on Thursday, with Corbyn’s statement co-signed by all of the Independent Alliance MPs bar Sultana: Ayoub Khan, Adnan Hussain, Iqbal Mohamed and Shockat Adam.That joint statement from all of the other MPs in the alliance prompted Sultana to claim she had been sidelined and excluded from key decisions.“Neither of this week’s emails had the dual authorisation of both myself and Jeremy – which was the agreement made at the start of this process,” she said in a statement posted on X on Thursday.

“After being sidelined by the MPs in today’s statement and effectively frozen out of the official accounts, I took the step of launching a membership portal so that the supporters could continue to engage and organise.”She added: “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.”Sultana also warned about power being concentrated in too few hands, intimating she was uncomfortable with the control being exerted by former Corbyn staffers from when he was leader of the opposition.

“I do not believe members will accept Karie Murphy [Corbyn’s former chief of staff] and her associates having sole financial control of members’ money and sole constitutional control of our conference,This undermines the democratic principles we agreed to uphold,”She called on Corbyn to meet her and “make public all agreed structures, processes and decision-making protocols”, adding: “This party is more important than any one person, and we all owe it to the movement to deliver a truly democratic and socialist party,No stitch-ups, no coronations: the members must decide,”Insiders have told the Guardian that allies of Corbyn have been asserting increasing control of the working group over financial and constitutional decisions, leaving Sultana pushing for a member-led structure.

But others said Sultana had been on “wrecking manoeuvres” and “sought after nothing but power”.An ally of the project said the row risked sending a “terrible signal to supporters still deciding if this project is serious”.It remains unclear whether the project will survive in the same form until its own founding conference in the autumn.