Image copyright PA Ken Livingstone should be "kicked out" of the Labour Party for defending an MP suspended over "anti-Semitic" comments, Sadiq Khan has said.
The London mayoral contender joined a growing chorus of Labour MPs calling for Mr Livingstone's expulsion.
But Mr Livingstone stood by his comments and said MP Naz Shah was not an anti-Semite.
He warned against "confusing criticism of Israeli government policy with anti-Semitism".
The former London mayor was accused by Labour MP John Mann of being a "Nazi apologist" as he arrived at the BBC's Westminster studios.
Naz Shah was suspended by the Labour Party, pending an investigation, over comments she made on Facebook before she became an MP, including a suggestion that Israel should be moved to the United States
She has apologised for the comments - but it has sparked fresh claims from senior Labour figures that the party is not doing enough to tackle growing anti-Semitism in its ranks.
Shadow Commons leader Chris Bryant told MPs: "I'm sick and tired of people trying to explain it away and yes, I'm talking to you Ken Livingstone."
Asked if Mr Livingstone should be suspended from the party, shadow mental health minister Luciana Berger replied "yes".
Labour's mayoral candidate Sadiq Khan said: "Ken Livingstone's comments are appalling and inexcusable. There must be no place for this in our party."
Explaining his stance, in his BBC News Channel interview, Mr Livingstone said: "Naz is not anti-Semitic - she was completely over the top, what she said was rude, but I literally, during the 47 years I've been in the Labour Party, I've never heard anyone say anything anti-Semitic.
"I've heard a lot of people being critical of Israel, but if I was to denounce the South African government, you wouldn't say I was racist.
"And one of my worries is this confusion with anti-Semitism and criticising the Israeli government policy undermines the importance is tackling real anti-Semitism."