Zarah Sultana has accused leading figures in the new party she is founding with Jeremy Corbyn of carrying out a "witch hunt" to purge left-wing activists.
Sultana boycotted the first day of the founding conference of the project, currently operating under the name Your Party, after several members who also belonged to the Socialist Workers Party were expelled.
Party officials said the expulsions were for breaching rules that ban members from joining any other political party in the UK or abroad.
Sultana's comments came as Corbyn used his conference speech to call for unity as the party had "a unique opportunity" to found "a socialist party of mass appeal".
