Jokes about disability in The Office and Extras were not sprung upon actors, but were "intrinsic to the script", comedian Stephen Merchant has said.

The way disability is portrayed has changed over the past 50 years, and Merchant said the jokes he and his comedic partner Ricky Gervais make are not exploiting disabled actors.

Merchant said his character in Extras, who makes fun of actor Warwick Davis, was "patently an idiot".

Are You Having a Laugh? Disability and TV is on BBC Two on Friday at 2100 BST.