Labour has suspended Jeremy Corbyn from the party over his reaction to a highly critical report on anti-Semitism.
The human rights watchdog found Labour responsible for "unlawful" harassment and discrimination during Mr Corbyn's four-and-a-half years as leader.
But he later said the scale of anti-Semitism within Labour had been "dramatically overstated" by opponents.
A Labour spokesman said Mr Corbyn was being suspended "for a failure to retract" his words.
Mr Corbyn reacted by calling the move "political" and promised to "strongly contest" it.
The suspension will remain in place while the party carries out an investigation into his remarks.
Sir Keir Starmer, who became Labour leader in April, said the publication of the Equality and Human Rights Commission's (EHRC) report had brought "a day of shame" for the party.
It found Labour responsible for three breaches of the Equality Act:
- Political interference in anti-Semitism complaints
- Failure to provide adequate training to those handling anti-Semitism complaints
- Harassment, including the use of anti-Semitic tropes and suggesting that complaints of anti-Semitism were fake or smears
The EHRC found evidence of 23 instances of "inappropriate involvement" by Mr Corbyn's office.
Sir Keir, who served under Mr Corbyn as shadow Brexit secretary, promised to implement the report's recommendations "as soon as possible in the New Year".
This seems not to have been a deliberately designed collision between the current party boss and his predecessor.
But this was an explosive political parting of ways, provoked in part by Mr Corbyn's trademark determination not to bend.
This is an attribute admired by many of his devotees, a frustration abhorred by his detractors and a sadness to those in Labour who believe it coloured the party's handling of anti-Semitism.
For Sir Keir, this episode does, perhaps by accident rather than design, prove beyond doubt his slogan - Labour is under new leadership - to be true.
Responding to the EHRC's findings, Mr Corbyn said he was "always determined to eliminate all forms of racism".
He claimed his team had "acted to speed up, not hinder the process" and that the scale of anti-Semitism within Labour had been "dramatically overstated for political reasons by our opponents inside and outside the party".
Shortly afterwards Labour general secretary David Evans suspended Mr Corbyn.
The party said this was "in light of his comments" and "his failure to retract them subsequently".
Mr Corbyn, Labour leader from 2015 until this year, reacted on Twitter, promising to "strongly contest the political intervention to suspend me".
He said those who denied the party had an anti-Semitism problem were "wrong" and he would "continue to support a zero-tolerance policy towards all forms of racism".
In an interview, Mr Corbyn did not retract his earlier comments and said: "I'll be appealing to the party and those who made the decision to kindly think again."
How events unfolded
10:00 GMT The EHRC releases its report saying Labour acted unlawfully over anti-Semitism
10:36 Jeremy Corbyn says there was an anti-Semitism problem in the party, but it was "dramatically overstated"
11:07 Sir Keir Starmer says those who think anti-Semitism is "exaggerated or a factional attack" are "part of the problem"
11:15 Sir Keir is repeatedly asked if he will expel Mr Corbyn for "exaggerated" comments - he says the report did not name individuals and repeats his previous statement
12:15 Mr Corbyn records an interview, to be released at 13:00, disagreeing with a number of the report's points and repeating that the number of anti-Semitism cases is "exaggerated"
13:06 Labour announces it has suspended Mr Corbyn
Sir Keir defended the decision to suspend Mr Corbyn, saying: "We cannot say 'zero tolerance' and then turn a blind eye."
He added: "I was very disappointed in Jeremy Corbyn's statement and appropriate action has been taken, which I fully support."
Sir Keir said would not "interfere" with the party's internal investigation into Mr Corbyn's statement.
Labour has been plagued by accusations of anti-Semitism since 2016, with a number of MPs quitting the party in protest while Mr Corbyn was leader.
Jewish Labour MP Dame Margaret Hodge said: "[The suspension] is the right decision following Corbyn's shameful reaction to the EHRC report."
The party was "finally saying enough is enough, anti-Semitism can never be tolerated", she added.
Labour deputy leader Angela Rayner told BBC Radio 4's World at One: "Jeremy is a thoroughly decent man, but he has an absolute blind spot and a denial when it comes to some of these issues."
But groups on the left of the Labour movement attacked the decision to suspend him.
The Socialist Campaign Group said it "firmly" opposed the move, adding: "We will work tirelessly for his reinstatement."
And Momentum, among Mr Corbyn's strongest backers, said: "It is a massive attack on the left by the new leadership and should be immediately lifted in the interests of party unity."
For the Conservatives, Cabinet Office Minister Michael Gove has written to Sir Keir, saying he "seemingly found it much harder to find the moral character and backbone to do what was right" while serving in the shadow cabinet under Mr Corbyn.
The EHRC launched its investigation last year after receiving a number of complaints from organisations and individuals, including the Campaign Against Anti-Semitism and the Jewish Labour Movement.