Naomi Watt has turned down an offer to star in her husband's new TV series Ray Donovan because she wants to keep her personal and professional life separate.

Live Schreiber is very keen for his wife to join the hit drama, in which he plays the titular character, a fixer for a law firm to the rich and famous.

However Watts has resisted his offers so far, insisting she wants to keep her personal and professional lives separate.

A source told The National Enquirer magazine: ''Naomi's made a point of distancing herself from Liev's career, and this is no different.

"She doesn't like to mix business with pleasure. Besides that, she knows Liev's show doesn't need her help.''

Ray Donovan has attracted big audiences in the US, with 1.35 million viewers tuning in to watch the premiere episode. It has already been commissioned for a second series.

Naomi, 44, and 45-year-old Liev - who have two sons, Sasha, six, and Samuel, four, together - are believed to have made an agreement with each other to avoid starring together on screen.

The source added: ''Naomi's not going to budge. She believes working on the show would kill their romance - and she thinks Live will thank her one day for turning him down.''