Jeremy Corbyn has not been invited to or was aware of a rally hosted by Zarah Sultana that is set to take place on the eve of the Your Party conference, his spokesperson confirmed to Sky News.
This is despite former Labour leader Mr Corbyn and ex-Labour MP Ms Sultana co-launching the party in July.
She has now announced a rally in Liverpool on Friday 28 November for those wanting an "unapologetically socialist, anti-Zionist, anti-imperialist programme".
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On social media, Ms Sultana called it "the eve of conference Your Party rally".
However, it is not an official Your Party event - and the tickets are being sold via her personal Action Network campaign.
A spokesperson for Mr Corbyn confirmed he was not aware of the event or invited to it, nor was anyone in his office.
It is understood the Islington North MP has no plans to hold a rally of his own.
Ms Sultana's event has prompted speculation of a de-facto leadership bid, ahead of a battle for the top job expected in the new year.
Members will vote on the leadership model at the conference, beginning officially on 29 November, but the idea proposed in the party's draft constitution is for a single leader rather than a co-leader model.
Independent MPs Mr Corbyn and Ms Sultana are yet to say if they will stand for the leadership, though both are widely expected to.
The speakers at Ms Sultana's event are figures seen as close to the Coventry South MP and her vision for the party, including Mish Rahman, a former Labour NEC member who is now active in the Democratic Bloc group.
Dembloc is a grassroots group of would-be Your Party members who have pushed for activists to have more say in Your Party. They have regularly tweeted in support of Ms Sultana and she spoke at an event they hosted on Monday night.
A spokesperson for Ms Sultana, who was stripped of the Labour whip last year for backing a move to scrap the two-child benefit cap, declined to comment.
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It is not clear if Mr Corbyn will do any events alongside Ms Sultana at all when members gather in Liverpool in just two weeks' time.
The Your Party conference programme is still being worked out and spokespeople for both sides were unable to provide clarity.
It follows months of factionalism and infighting at the heart of what promised to be a major moment for the British left but has so far been dominated by rows over leadership, finances and even its name.
This has broadly involved two factions - those close to Mr Corbyn who have worked with the former Labour leader for many years, and those close to Ms Sultana who see her as a fresh face for the British left.
Your Party says it has 50,000 paid members - but only a fraction will be able to attend the conference after being chosen through a sortition.
(c) Sky News 2025: Jeremy Corbyn was not invited to Zarah Sultana rally on eve of Your Party conference
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