The star was famous for his role as Captain Peacock in Are You Being Served? and as Truly in Last Of The Summer Wine.
"Ninety-two-year-old Frank Thornton died peacefully in his sleep on Saturday," his agent said.
"Frank was a much loved British actor who played mainly comedy roles and is perhaps best known for his role as Captain Peacock in Are You Being Served? and latterly as Truly in Last Of The Summer Wine.
"Frank is survived by Beryl, his wife of 67 years, daughter Jane and their three grandchildren.
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"I have been Frank's agent since 1986 and he has been the most wonderful client as well as being a great friend. He will be sorely missed."
Sitcom star Thornton was the last of the original main members of the cast of Are You Being Served?. He also went on to appear in its successor series, Grace & Favour.
In more recent years he was familiar to viewers for his role as Truly in long-running Last Of The Summer Wine, alongside a roster of veteran comedy actors.
He specialised in comedy and over the years took roles in many popular TV shows including Hancock's Half-Hour, Sykes and Steptoe And Son, as well as movie spin-off Steptoe And Son Ride Again.
Thornton also appeared in a number of saucy British movie romps including No Sex Please, We're British and Up The Chastity Belt.
In 2001 he was among the cast for the Julian Fellowes-scripted period drama Gosford Park.
His last credit was in the poorly received British film Run For Your Wife, alongside Richard Briers, who died last month.
Thornton, who was born in Dulwich, had worked in insurance after leaving school but studied to become an actor with evening classes, eventually leaving his job to study full time.
He made his professional stage debut in 1940 with a production of French Without Tears in Ireland.
The moustachioed star was soon appearing on the West End stage in Shakespeare roles, as well as the 1942 production of Terence Rattigan's Flare Path.
He went on to serve in the Royal Air Force during the Second World War and after demob went into rep theatre. By 1954 he had picked up his first film credit in the crime movie Radio Cab Murder.
By the 1960s he was becoming a familiar face with roles in movies such as Carry On Screaming, but it was in the 1970s that he became a household name with the huge success of Are You Being Served?, which ran from 1972 to 1985.
Nicholas Smith, who featured alongside him in the department store sitcom, paid tribute to Thornton saying: "He was the best actor in Are You Being Served?"
Thornton continued to have stage success with a well-received run in Me And My Girl in the West End, and many touring productions.
