The National Schizophrenia Fellowship says 45% of health authorities are rationing the new drugs which are often more effective and can prevent four in five suicides by schizophrenics.

The older anti-psychotic drugs often cause side-effects such as facial tics, shaking and problems controlling the tongue which increase the stigma attached to schizophrenia.

Mental health workers say people tend to associate these symptoms with schizophrenia rather than with the drugs.

However, the older drugs are much cheaper than the new ones.

Mental health charity Sane says a yearly course of the new atypical drugs costs £2,000 per person, compared with £20 a person for a course of the old ones.

It conducted its own straw poll of psychiatrists in four parts of the country earlier this year.

The charity found 77% of psychiatrists said that the new drugs were being rationed in the hospitals where they worked.

Benefits

"It is definitely based on cost," said a spokeswoman. "There is a very, very big difference in cost, but we believe the benefits to patients outweigh the costs."

A recent report by Dr Jonathan Hellewell, consultant psychiatrist at Trafford General Hospital in Manchester, found that the side-effects associated with older anti-psychotic drugs were a big factor in patients deciding to discontinue their medication.

Mental health workers say this can lead to patients being at an increased risk of breakdown and relapse.

Sane says many may end up in hospital as a result, when they could be treated more cheaply in the community.

Stress

According to the Health Education Authority (HEA), around one in 100 people in the UK will experience an episode of schizophrenia in their lifetime.

A quarter will recover fully, but up to 15% will have enduring problems.

It is thought that schizophrenia is triggered by a mixture of social and personal factors, including stress, taking illegal drugs and genetic causes.