Powerful anti-psychotic drugs intended to treat schizophrenia are reportedly being regularly used to “chemically cosh” elderly dementia patients.

Sube Banerjee, professor of mental health and ageing at the Institute of Psychiatry at King’s College London, has said people are being kept on the drugs for far too long.

His warning echoes research suggesting such drugs can double the risk of death and triple the risk of stroke.

Professor Banerjee said: “This is a major NHS issue. There are a lot of people treated with drugs that are potentially harmful.”

The drugs are prescribed to control symptoms such as aggression, agitation and hallucinations, but critics say they are often given to sedate people.

A government review estimates that 180,000 people with dementia are thought to be on the medicines, with only around 36,000 getting any benefit. Overprescribing is linked to 1,800 deaths a year.