Keir Starmer has claimed the swift suspension of Diane Abbott over "anti-Semitic" comments demonstrates Labour's "zero tolerance" approach.
The Labour leader condemned a letter published under the MP's name on Sunday which suggested Jewish, Irish, and Traveller people are not subject to racism "all their lives".
"They undoubtedly face prejudice," the MP wrote. "This is similar to racism and the two words are often used as if they are interchangeable".
After the comments provoked widespread criticism, Ms Abbott issued a public apology for any "anguish" caused and said an "initial draft" of her letter was sent in error.
She added: "Racism takes many forms, and it is completely undeniable that Jewish people have suffered its monstrous effects, as have Irish people, Travellers and many others."
But on Sunday a Labour spokesman confirmed the whip had been removed from the veteran MP - pending an investigation - over the "offensive" remarks.
Speaking on Monday Mr Starmer highlighted the vile racist abuse received by Ms Abbott over her career in Parliament - spanning from 1987.
But he said: "That doesn't take away from the fact that I condemn the words she used and we must never accept the argument that there's some sort of hierarchy of racism".
The Labour leader added: "In my view what she said was to be condemned, it was anti-Semitic.
"It's absolutely right that we acted as swiftly as we did. That's the change we've seen in the Labour Party.
"But do I condemn what she said? I absolutely condemn what she said".
He refused to be drawn on whether Ms Abbott - the first black woman elected to Parliament- would be prevented from standing for the party at the next election.
He added: "There's an investigation in place, I've got to let that investigation be completed."
Earlier Pat McFadden, the Shadow Chief Secretary to the Treasury, said the party had "no choice" to take action against the veteran Labour MP.
He said: "They were offensive to people and based on a very wrong idea that there can be some sort of hierarchy when it comes to victims of racism.
"Anyone who has looked at the history will know that Jewish people have suffered the most terrible racism. The history of the 20th century is very obvious."
Former Labour adviser under ex-PM Tony Blair, John McTernan, also highlighted that Ms Abbott has been at the receiving end of racism.
He said on social media: "Swift and appropriate apology from Diane Abbott.
"She has been subjected to vile racist abuse throughout her career, and her apology should be accepted in the spirit it is offered".
