The number of British children being given controversial anti-psychotic drugs has increased sharply, according to research.

As many as 3,000 children were administered the unlicensed drugs between 1996 and 2005, despite concerns from experts that they could cause long-term harm and even death.

Doctors gave out twice as many prescriptions for the medication in 2005 as in 1992, even though they are not licensed to be given to children.

The number of prescriptions for children in the 7 to 12 age group trebled, the largest area of expansion, according to findings by Ian Wong, a Professor of Paediatric Medicines Research at the London School of Pharmacy.

In most cases, the drugs have been given to children with behavioural and personality disorders, autism and hyperactivity.

The research is to be published in the US journal Pediatrics next month. David Healy, Professor of Psychological Medicine at Cardiff University gave warning that the drugs could cause heart, circulatory and breathing problems.

"There is a real question over whether the drugs can kill, for a number of reasons," he told The Guardian. "One is that all anti-psychotics act on the dopamine." Professor Healy said that dopamine was known to have a role in cardiovascular regulation.

The Medicines and Healthcare products Regulatory Authority is concerned about the use of the drugs in the absence of evidence to prove that they are safe to be given to children. However, it cannot act unless trials are conducted by manufacturers.

The increased use of the drugs in this country follows a huge rise in their use in the United States.

Professor Wong contends that children on anti-psychotic medication are more likely to die prematurely, something which may not be caused by the drug itself. "The mortality rate is much higher," he said "It could be some underlying problems of the brain. It doesn't show the drug is causing any deaths but there is this inequality."

Professor Wong said that he was aware of a number of deaths of children with underlying incurable conditions such as Aids, so it was hard to establish whether the drugs played a part.

The increase in the use of the drugs has come at a time when Prozac and other similar drugs used to treat depression have gone out of patent.

In the US, the prescription for children of anti-psychotic drugs has increased along with the trend for behavioural problems to be diagnosed as manic depression.