Jeremy Corbyn is facing legal actionover his statement in relation to the settlement of the BBC Panorama libel claim.
Mark Lewis, of Patron Law, confirmed he was representing the journalist John Ware in the legal action. Some of the antisemitism whistle-blowers have also joined the action.
Mr Lewis said: “I confirm I have been instructed to pursue cases.”
In a statement on social media on Wednesday, Mr Corbyn said: “The party’s decision to apologise today and make substantial payments to former staff who sued the party in relation to last year’s Panorama programme is a political decision, not a legal one.
“Our legal advice was that the party had a strong defence, and the evidence in the leaked Labour report that is now the subject of an NEC inquiry led by Martin Forde QC strengthened concerns about the role played by some of those who took part in the programme.
“The decision to settle these claims in this way is disappointing, and risks giving credibility to misleading and inaccurate allegations about action taken to tackle anti-Semitism in the Labour Party in recent years.
“To give our members the answers and justice they deserve, the inquiry led by Martin Forde must now fully address the evidence the internal report uncovered of racism, sexism, factionalism and obstruction of Labour’s 2017 general election campaign.”
Mr Lewis had represented the whistle-blowers and Mr Ware in their settlement with Labour, which was confirmed in the High Court after the party issued a formal apology and agreed to pay substantial damages.