Prescriptions of Methylphenidate - most commonly sold as Ritalin - rose to 359,100 last year, a rise of 344,400 since 1995. Figures from the Prescriptions Pricing Authority reveal that there has been a 180-fold increase in prescriptions since 1991 when only 2,000 were issued in England.

The growing use of Ritalin - an amphetamine-based stimulant which improves concentration and is nicknamed the "chemical cosh" because of its calming effects - has alarmed critics. It is almost entirely prescribed to children under 16 in this country. Controversially, it has been estimated that one in 20 children suffers behavioural disorders such as attention-deficit hyperactivity disorder or ADHD, for which Ritalin is prescribed.

But critics of the drug say that doctors give it to children who are merely displaying normal emotional changes experienced during childhood. Campaigners believe that the increasing use of Ritalin follows the trend in America where it has been prescribed to children as young as 15 months.

Last night, the Citizens Commission on Human Rights, an organisation that campaigns against psychiatric violations of human rights, condemned the increasing prescription of drugs for children. "Too many psychiatrists are being irresponsible in prescribing mood-altering drugs which are pharmacologically similar to cocaine, and then claiming they have 'cured' children of their 'condition'," said a spokesman.

"Some children may be a little boisterous but psychiatry's fixation on labelling such difficulties and prescribing medication is nothing more than pseudo science. Children are being drugged into submission."

There are currently no medical tests for ADHD and children are diagnosed on the basis of their behaviour and questionnaires that ask if a child displays symptoms including restlessness, inattentiveness and fidgeting. Sami Timimi, a consultant child expert and adolescent psychiatrist based in Lincolnshire, described the soaring use of Ritalin as "a scandal" and insisted that the drug should be used only as a last resort.

"It is ludicrous that the normal spectrum of behaviour that all kids will demonstrate at some time in their childhood is now interpreted as a disorder which requires medication," he said.

"Various methods of behaviour management therapy and a change in diet are often all a child needs but adults are increasingly turning over the role of parenting to professionals who feel more "doctory" if they can make a diagnosis and prescribe medication."

Dr Timimi said that not enough parents were aware of the potential health risks and side-effects associated with Ritalin, which include loss of appetite, insomnia and unresponsiveness.

A recent survey that compared international prescription rates for children of antidepressants and mood-altering drugs including Ritalin showed that Britain has the highest rate in the world.

Research in the United States found that Ritalin may cause lasting changes to the brain. In a study carried out by the Harvard Medical School, healthy rats given the drug in their infancy were found to have a reduced sense of pleasure and were more prone to signs of despair during adulthood.

Prof Sir Alan Craft, the president of the Royal College of Paediatrics and Child Health, said that the growing use of Ritalin was "concerning".

Prof Peter Hill, an ADHD specialist and honorary consultant in child psychiatry at the Great Ormond Street Hospital in London, believes that the concept of ADHD has become popular, "partly because it offers an alternative explanation for antisocial behaviour, other than imperfect parenting".

"While Methylphenidate undoubtedly works for some children, clinicians are under increasing pressure from vast waiting lists to see people as quickly as possible, resulting in some medicating where it is perhaps not necessary," he said.

"I have children coming to me who have been prescribed all sorts of medication without much preparatory work-up."

Janice Hill, the founder of the Overload Network, a charity that campaigns against the prescription of drugs to children, said that parents were not being given enough information on alternative treatment. "Doctors are far too quick to medicate drugs as a quick-fix answer, instead of recommending therapy or properly analysing the root causes of a child's anxiety," she said.

Sam James, an eight-year-old schoolboy from Reading, was diagnosed with ADHD and prescribed Ritalin when he was just two years old, after showing symptoms including fidgeting and constant screaming.

However, his mother was so shocked by the effects of the drug that she took him off the medication after four weeks.

"The results were unbelievably horrific," said Mrs James, 34. "Within a matter of weeks Sam went from being a lively boy to a zombie who sat on a chair in the corner rocking.

"He became completely withdrawn and uncommunicative and I could hardly recognise him as my son."

After taking him off Ritalin, which costs around £6 for one month's supply, Sam's psychiatrist, who has since been struck off the medical register, prescribed yet another sedative over the telephone, which Mrs James did not give to her son.

"We found that using cognitive behaviour therapy and just talking to our son has been much more helpful than medication," she said.

"Having seen the effects of Ritalin on Sam, I would advise parents to try any other avenue before resorting to drugs."