Katherine Heigl is reportedly planning to quit hit US TV show Grey’s Anatomy to concentrate on her film career.

The actress — who shot to fame playing Dr. Isobel Stevens on the show — has since found success in romantic comedies ‘Knocked Up’ and ‘27 Dresses’ — and is now said to be keen to end her contract with Grey’s to focus entirely on movies.

A source close to the actress said: “She’s working really long hours and is ready to move on. She’s a smart one.

“She saw what can happen with someone like Jennifer Aniston, who was crazy successful on TV, but can’t seem to carry a film, and she tested the waters early.”

However, Katherine — whose negotiations for her contract renewal on the show were made public 15 months ago — may be locked into her contract and will have to continue starring in the hit medical drama.

The source added to Us Weekly magazine: “I don’t think she’ll be able to get out of it.”