America's highest-rating sitcom has been cancelled following a racist tweet by its biggest star.

Disney's ABC network is cancelling the sitcom Roseanne after an abhorrent and repugnant tweet by Roseanne Barr.

Barr compared Iranian-born Obama White House adviser Valerie Jarrett to an ape.

CNN media expert Brian Stelter says the Disney-owned network is giving up billions of dollars in revenue, to avoid billions of dollars in reputational damage.

"I think what this means, I think what ABC is trying to do here, is make a statement about what is appropriate and what is going to be acceptable in mainstream America."

The show airs on Three in New Zealand.