MORE children are likely to be diagnosed with attention deficit/hyperactivity disorder if controversial changes to the way the disorder is diagnosed are implemented, critics say.

Under proposed changes to the most influential psychiatric prescribing manual, the DSM, which is being revised this year, instead of a child needing to display 12 of 18 symptoms they will need 12 of 24.

Martin Whitely, a Western Australian politician and former school teacher who campaigns against over-medication and diagnosis of ADHD, is concerned the expanding criteria for the disorder would increase the number of children diagnosed.

Some of the new symptoms include a tendency to act without thinking and finds it difficult to resist temptations and opportunities. "I tend to act without thinking and I'm often impatient as well," he said. "It's just this process of ever lowering the bar for diagnosis."

In a published ''pros and cons'' list about the additional symptoms, the committee said they were "not empirically derived" and had potential to decrease the accuracy of the criteria.

Melissa Raven, a psychiatric epidemiologist and policy analyst at Flinders University, in Adelaide, said that was an "absolutely damning statement".

"They have identified some problems then proceeded blithely on," she said.

Allen Frances, the chairman of the taskforce that produced the present edition of the DSM, said when they increased the number of symptoms they produced an ''epidemic'' of ADHD. They thought it would increase by 15 per cent, but it actually increased by 200 per cent.