The National Institute for Clinical Excellence will publish its judgement over the use of the drugs, known as atypical antipsychotics, on Thursday.

The drugs, including risperidone, quetiapine, clozapine and olanzapine, cause considerably fewer side-effects than older antipsychotics such as haloperidol.

Atypicals are significantly more expensive, however.

People have not been given the choice of medication for schizophrenia, leaving many to struggle with the stigmatising and damaging side-effects of the older medications

Marjorie Wallace, SANE

Campaigners estimate that, at the moment, just 20% of people with schizophrenia who could benefit from the drugs actually receive them.

If, as expected, NICE does approve the drugs for NHS use, the medicines bill could increase by around �100m.

The old type of drug costs around �70 a year whereas the atypicals cost around �1,220.

But there would be savings made because there would be reductions in hospital admissions.

Choice for patients

The National Schizophrenia Fellowship (NSF) has surveyed people using the drugs.

It found 92% had experienced side-effects from older drugs - such as muscle spasms, shaking and weight gain.

The drugs had affected 43% of people's ability to carry on with everyday life "a lot".

Almost half taking the older type drugs had stopped taking their medication at some point, without the backing of their doctor, compared to just one in three taking the newer types.

Better quality of life

A spokesman for the NSF told BBC News Online he hoped NICE would end "rationing that's been in existence since the drugs became available 10 years ago."

He added: "It would enable clinicians around the country to prescribe the drugs which they think are the best.

"But most importantly, it would enable people with schizophrenia and their carers to access the medications they feel are better for them and strengthen their chances of getting stronger, of having a better quality of life."

Marjorie Wallace, chief executive of SANE, said: "To date, people have not been given the choice of medication for schizophrenia, leaving many to struggle with the stigmatising and damaging side-effects of the older medications.

"The newer drugs may have their own side-effects, but we have lobbied for them to become more widely available because it is our experience that they enable many more people with psychotic illnesses to lead a more fulfilling life."