The Prime Minister has been called a "racist" by opposition MPs after wading into the extremism row embroiling Labour's mayoral candidate Sadiq Khan.
During Prime Minister's Questions, David Cameron accused Mr Khan of repeatedly sharing a platform with an Islamic State supporter
The PM struggled to make himself heard when his claim was met with shouts of "racist" from the Labour backbenches.
The incident came after former Labour minister Yvette Cooper said Conservative London Mayor hopeful Zac Goldsmith's "subtle dog-whistle is becoming a full-blown racist scream".
Mr Cameron said: "If we are going to condemn not just violent extremism but also the extremism that seeks to justify violence in any way, it is very important that we do not back these people and we do not appear on platforms with them.
"And I have to say I am concerned about Labour's candidate as Mayor of London, who has appeared again and again and again..."
Mr Cameron was cut off by loud roars from the Labour Party, before adding: "The leader of the Labour Party is saying it's disgraceful. Let me tell him.
"Sulaiman Ghani, Mr Khan has appeared on a platform with him nine times.
"This man supports IS. He even shared a platform... I think they are shouting down this point because they don't want to hear the truth.
"Anyone can make a mistake about who they appear on a platform with. We're not always responsible for what our political opponents say. But if you do it time after time after time it is right to question your judgment."