Drug users are experimenting with newly-invented psychoactive drugs because they cannot get more ''traditional'' products such as ecstasy, a study has found.

Drug experts say Australia must abandon its attempts to stay one step ahead of the illegal drug producers, and follow New Zealand's lead in testing newly invented drugs for safety and then allowing them to be sold. A study of more than 680 people who use drugs such as ecstasy and speed has found nearly half of them had tried new synthetic drugs, which attempt to mimic the effects of known drugs but have a different molecular make-up.

National Drug and Alcohol Research Centre researcher Lucy Burns said people try emerging drugs out of curiosity, or because they are having trouble getting the substances they would usually take.

''When a new set of drugs are raised or being used it's because traditional markets of drugs decline,'' she said. Often users had no idea what substance they were actually taking.

There was a decline in ecstasy availability in the past two years when the research was conducted but there has been a resurgence.

She said drug manufacturers are inventing substances to stay one step ahead of the law.

"It's a very rapid market,'' she said.

But the study found despite many websites selling the newly invented drugs, the vast majority of users were still taking drugs bought from a dealer or a friend.

The head of the Australian Drug Foundation, John Rogerson, said the government should reconsider its synthetic drug strategy as it left regulators "constantly on the back foot" reacting to new substances.

Correction: The original story incorrectly named the head of the Australian Drug Foundation as John Robertson.