The veteran star said delays in commissioning his popular series Inspector George Gently, as well as the to-ing and fro-ing with scripts, meant the stars had often taken on other work by the time they were approved.
In a magazine interview Shaw, also known for The Professionals and Judge John Deed, said he was unsure about the future of Gently. "We don't know if there will be an eighth series. They'll wait to see our ratings and then if they do recommission, it will be too late," he explained.
"The pressure is on to write four films quickly, and once they're finished, it's passed up the food chain. By the time it's gone through everyone, the writers are tearing their hair out."
He suggested viewers would prefer to see older characters on screen, saying: "Older people stay home to watch. The young go out."