The SNP Westminster leader was asked by the Speaker to withdraw claims of racism about Boris Johnson.
Ian Blackford read out some comments he attributed to the Tory leadership candidate, and after a warning from John Bercow, asked: “If that is not racist, Mr Speaker I don’t know what is.”
He added Mr Johnson was “not fit” to be PM.
Theresa May said Mr Blackford did not understand the purpose of PMQs. which was to ask the PM about government actions, but any Conservative leader “would better for Scotland” than the SNP.