Ken Livingstone’s party expulsion hearing has been told that the former Labour mayor of London brought the party into disrepute by suggesting Adolf Hitler had supported Zionism, assertions Livingstone repeated at length to reporters outside the meeting on Thursday morning.

Before the hearing by Labour’s highest disciplinary body, Livingstone addressed reporters, claiming there had been “real collaboration” between the Nazis and Jews.

“[Hitler] didn’t just sign the deal,” Livingstone said. “The SS set up training camps so that German Jews who were going to go there could be trained to cope with a very different sort of country when they got there [Palestine].”

The hearing by Labour’s national constitutional committee (NCC), the only body with the power to expel members, will continue into Friday, when the panel will make a decision.

Livingstone had pledged he would present historical analysis to back up his claims in a series of TV and radio interviews that Hitler “was supporting Zionism” before he “went mad”. He is also understood to have argued on Thursday that the case against him was motivated by a plot to undermine Labour leader Jeremy Corbyn and his supporters in the party.

Livingstone’s comments refer to the Haavara agreement signed by the Nazi government which facilitated the relocation of some Jews to Palestine in 1933, before the Third Reich began its mass extermination.

However, Livingstone’s claim that the agreement had meant Hitler was supportive of a Jewish homeland has been widely disputed by historians including Prof Richard Evans, the expert witness for the defence in the high-profile libel case brought by Holocaust denier David Irving.

Livingstone, who has been suspended from the party for 11 months, told reporters that the Nazis sold weapons to Zionist fighters and set up training camps to help Jews adapt to life in a different country. “So you had, right up until the start of the second world war, real collaboration,” he said.

Labour’s general secretary, Iain McNicol, made it clear in a letter to the former mayor that the case against him was not about the historical facts, but whether his conduct was “grossly detrimental” to the party, especially given his defence of antisemitic Facebook posts by Bradford West MP Naz Shah. She has since apologised for the posts.

Livingstone claimed the Labour party was no longer investigating him over antisemitism or the claim that Hitler was a Zionist, but focusing on the accusation that his defence of Shah had brought the party into disrepute. He said he had hoped the meeting could be held publicly.

“It’s completely unfair,” he said. “We have a tradition of law and that is open. There’s absolutely no justification for something like this being done in private.”

The Jewish Labour Movement, whose chair Jeremy Newmark was called as a witness to the hearing on Thursday, is understood to have submitted a 170-page dossier on the incidents leading up to the expulsion hearing. Among those believed to be quoted in the document condemning Livingstone’s comments are the chief rabbi, Ephraim Mirvis, and other senior rabbis of the Orthodox and progressive movements.

Two leading QCs are presenting the cases for each side. Livingstone’s barrister is Michael Mansfield, who has represented families of victims at the Bloody Sunday inquiry and advised Corbyn during the legal challenge to the party’s leadership election last summer.

Labour’s national executive committee, which referred the case to the NCC, is being represented by Clive Sheldon QC, who successfully defended the party at the court of appeal for its right to bring in £25 registered supporter fees after a challenge by members during last summer’s leadership contest.

Livingstone has submitted five witness statements from Jewish Labour party members in his defence, all five of whom are involved in anti-Zionist and Palestinian rights activism, including LSE professor Jonathan Rosenhead, the founder of the campaign to boycott Israeli universities. All five are understood to be appearing in person.

As well as Newmark’s evidence, the NEC has assembled statements from polling and campaigning experts to give their views on the effects of Livingstone’s statements on the party’s electoral performance.

The NCC has 11 members – long-time Labour activists, councillors and trade union representatives – and is chaired by Rose Burley, a Labour member for 52 years, who presided over the expulsion of George Galloway.

Newmark would not comment on what had taken place in the hearing, where he was cross-examined by Mansfield, but criticised Livingstone’s remarks earlier on Thursday. “He continues to dig himself a hole, even outside his own expulsion hearing, with his misreading of the history of the Holocaust.”

Karen Pollock, the chief executive of the Holocaust Educational Trust, said Livingstone’s comments on Thursday showed he was unrepentant about the hurt he had caused. “Even when it has been made blatantly clear that his comments have caused deep hurt and offence to Jewish people, and in particular to Holocaust survivors, still Ken Livingstone has persisted down this route – repeatedly invoking the Holocaust, promoting a misleading and misinformed version of history to further his agenda,” she said.