Labour activist Jackie Walker has been expelled from the party after she was accused of anti-Semitism.
Ms Walker has been suspended for three years over alleged anti-Semitic remarks.
A Labour spokesman said: "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."
Joe Glasman, of the Campaign Against Antisemitism, 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 Antisemitism brought in the Equality and Human Rights Commission 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."
Reacting to the news, Labour MP for Brimingham Yardley Jess Philips tweeted: “Good”.
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.
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 that she had been denied the opportunity to make a statement.
