Labour activist Jackie Walker has been expelled from the party.
Ms Walker’s case has become a subject of fierce internal controversy within Labour since her suspension almost three years ago.
The activist, who is herself part-Jewish, has conducted a vigorous campaign in her own defence, including a one-woman show entitled The Lynching in which she denied being anti-Semitic and accused her critics of engaging in a witch hunt.
Leading left-wing MP Chris Williamson was criticised by party officials for arranging a screening of a film about her in Parliament, just days before his own suspension for claiming Labour had overreacted to anti-Semitism allegations.
Ms Walker was removed as vice-chair of the Jeremy Corbyn-supporting Momentum movement shortly after the allegations against her first emerged in 2016.
She was accused of linking Jews with the Atlantic slave trade in a social media post and of making anti-Semitic comments during a training session on confronting anti-Semitism at Labour’s annual conference.
On Tuesday, she pulled out of a disciplinary hearing of Labour’s National Constitutional Committee (NCC), claiming she had been denied the opportunity to make a statement.
A Labour spokesman said today: “The National Constitutional Committee has found that the charges of breaches of party rules by Jackie Walker have been proven.
“The National Constitutional Committee consequently determined that the sanction for this breach of the rules is expulsion from Labour Party membership.”
The NCC is an autonomous body independent of the party’s staff and leadership and is the only body with the power to expel members.
Once a complaint is referred for an NCC hearing, the case against the individual is prepared and prosecuted by the party, but the decision is in the NCC’s hands.
It is understood the case against her, presented behind closed doors, relied on a pattern of behaviour over a period of time, including many comments on social media.
Joe Glasman, of the Campaign Against anti-Semitism, claimed that Labour had been prompted to act in the long-running case by the decision of the Equality and Human Rights Commission earlier this month to launch an enforcement process to look into claims of anti-Semitism in the party.
“It comes as no surprise that the institutionally anti-Semitic Labour Party waited almost three years to finally expel Jackie Walker,” Mr Glasman said.
“During those three years, she has toured the nation, openly supported by leading Labour MPs, claiming that the case against her was trumped up.
“It is because Labour has shown itself to be incapable of addressing anti-Semitism cases in a fair, transparent and timely manner that Campaign Against anti-Semitism brought in the EHRC to take charge.
“Labour’s decision to finally act, now that the commission is at the gate, is not a sign of change, but merely an act of naked self-preservation by a political party being brought face-to-face with its own racism.”
The decision comes after Labor’s National Constitutional Committee found that charges against her were proven.
Ms Walker had been suspended for three years over allegedly anti-Semitic remarks.