Former Cheers star Kirstie Alley still regrets falling in love with late actor Patrick Swayze on the set of Tv mini-series North & South because both stars were married.

The actress insists she never acted on her feelings for the Ghost star because she didn't want to break up his marriage to dancer Lisa Niemi - but she still feels bad about falling for Swayze, who played her husband on North & South.

In a new expose on U.S. news show Entertainment Tonight, she explains, "Both of us were married. We did not have an affair. But again, I think what I did was worse.

"I think when you fall in love with someone when you're married, you jeopardise your own marriage and their marriage. It's doubly bad."

Her revelation might come as a big surprise to Niemi because Alley, who was asked to speak at Swayze's funeral by his widow, isn't sure if she was aware of her deep feelings for her husband.