The head of the Bethlem Royal Hospital in England has asked the Perth Royal Show to withdraw a controversial attraction based on the mental health institution, claiming it is "deeply offensive".

Debuting at this year's show, the Bethlem Sanatorium ride features an open ward with 20 actors pretending to be patients from the notorious hospital, commonly known as Bedlam.

The institution, the first of its kind in Britain, was founded as a hospital in the 13th century and was known for its cruel treatment of patients.

It is still in operation, providing specialist mental health facilities for more than 450,000 patients a year.

Matthew Patrick from the South London and Maudsley Foundation, which runs the hospital, wrote to Royal Agricultural Society head Peter Cooper to request that the attraction, listed as "Sideshow Fun" in the kids and family section of the show's website, be removed.

"The ride is deeply offensive; stigmatises mental illness and reinforces negative stereotypes about mental health," he wrote.

"It fosters discrimination and promotes the perception of 'scary mental health patients' which will undoubtedly deter people from seeking the help they need."

He said the hospital depicted in the attraction was "not merely an historical or fictitious institution" but "a real place, with real patients who are experiencing real illness".

"I realise that the ride at your show is satirical and designed to appeal to a sense of fun, but there are ways of doing this without causing such offence or referring to an existing hospital and its patients," Dr Patrick wrote.

"We ask that you cancel this ride so that it is not included in the show and does not cause detriment to our hospital, staff and most importantly to our patients and other people with mental health difficulties."

The WA Mental Health Association, the Consumers of Mental Health group and WA Mental Health Minister Helen Morton have all condemned the ride.

A spokeswoman for the Royal Agricultural Society said it would be meeting later today to review the issue.