Keir Starmer and Sadiq Khan at the Labour conference in Liverpool last year.Keir Starmer has slapped down Sadiq Khan by insisting the chant “from the river to the sea, Palestine will be free” is anti-semitic.The prime minister’s comments came just days after the London mayor insisted it was not.The chant is regularly sung at pro-Palestine marches and is widely interpreted as a demand for Israel to no longer exist.During mayor’s question time last week, London Assembly member Susan Hall asked Khan directly if the chant was anti-semitic.He said: “I don’t think it’s anti-semitic. I think it’s all about context.”But asked by the Jewish Chronicle on Thursday whether it was anti-semitic, Starmer replied: “Yes.”When it was pointed out to him that Khan took a different view, the PM said: “I take a strong on this and we’ve dealt with cases in my own party where people have used that expression and we’ve taken action against them.“I’m not just saying it to you today, that is the history, that is the record, that I have as leader of my party.”