The actress, who has played Sgt June Ackland since its pilot in 1983, is the only original cast member still remaining on the show.
Speculation over her exit has been rife for some time but rumours appeared to be quashed recently when she signed a one-year contract extension.
“Trudie has been thinking for a while about leaving The Bill and has finally made the difficult decision," a source told The Sun today. “She has signed a new contract which takes her up to the end of the year, but has told producers it will be her last.
“She’d like them to come up with a real slow-burner of a plot leading to her exit. They’re in talks now. It promises to be absolutely huge.”