One of the world's biggest pop stars has taken the stand in a case where she says she was groped by a radio DJ.

Taylor Swift said she was subjected to a very long and intentional grope by a Colorado disc jockey, who appeared to be drunk during a photo session.

US correspondent Richard Arnold told Mike Hosking David Mueller said he was fired after Swift's people complained to his boss.

"She says he grabbed her underneath her skirt, something she said was not seen by others because they were taking a photo and had their backs to the wall."

Mueller has already testified, saying he may have made innocent contact with Swift but denies any inappropriate behaviour.

LISTEN ABOVE AS DAVID MUELLER SPEAKS WITH MIKE HOSKING