Prince William made the comment during his first public appearance since claims of bigotry and a lack of support were levelled at the royal family by Harry and Meghan in their interview with US chat show host Oprah Winfrey.
He and the Duchess of Cambridge toured School21 in Stratford, east London, to mark the return of children to classes this week and the rollout to secondary schools of a mental health project Kate Middleton launched in primary schools in 2018.
As Prince William left, a reporter asked him: "Is the royal family a racist family, sir?"
The duke replied: "We're very much not a racist family."
Buckingham Palace has said that the claim a Royal Family member questioned the Sussexes’ unborn baby’s skin colour was ‘concerning’ and the matter will be handled ‘privately.’