London mayor Sadiq Khan said comments made by London MP Rupa Huq about the chancellor were “racist” but insisted she herself is not.
The Ealing MP described Kwasi Kwarteng as “superficially” black during an event at the Labour Party conference.
Mr Khan told BBC Radio London the comments were "wrong" but added Huq was "not racist".
Talking about Mr Kwartang, she also said: “If you hear him on the Today programme you wouldn’t know he’s black."
Mr Khan said: “What it infers is that all black people speak a certain way and all black people are working class.
"Rupa is not racist but that comment was."
His comments echo those of Labour leader Sir Keir Starmer who welcomed the party taking “very swift action” in suspending Ms Huq’s membership after her remarks were revealed.
Sir Keir told LBC Radio: “What she said, in my view, was racist, it was wrong and she’s been suspended from the whip in the party and that was done very, very quickly.
“I think that tells you how strongly I feel about those comments.”
Ms Huq offered a “sincere and heartfelt” apology to Mr Kwarteng over her “ill-judged” comments after being criticised by senior Labour figures.
The MP for Ealing Central and Acton in west London was administratively suspended from the party, and therefore lost the party whip, after audio was published online.