RECREATIONAL drug users have been warned about a highly toxic imitation of ecstasy following a spate of deaths in the UK from 'Dr Death' ecstasy pills.

Five young people have died over the past month in parts of the UK, reports the Daily Mail, after taking what they believed to be ecstasy, but in fact contained the dangerous substance PMA.

PMA, or para-Methoxyamphetamine, is a "synthetic amphetamine-type drug with both stimulant and hallucinogenic properties", according the Australian Drug Federation.

The Drug Squad says it's almost exclusively as MDMA - or ecstasy - posing a huge risk to recreational drug users.

It's more dangerous than regular ecstasy because it's known to cause death and takes longer to affect the brain - meaning users are more likely to double or even triple their dose.

Though PMA has been a problem in Australia before - six deaths were attributed to the drug being sold as ecstasy in South Australia in 1998 - experts warn that young people need to be extra vigilant.

"With any manufactured drug there is no guarantee of quality or quantity," said a spokesperson for the NSW Drug Squad.

"You don't know the dosage you're taking, or what you're actually taking.

"You're basically in the hands of criminals who are trying to turn a profit rather than looking out for your safety."

The Australian Drug Federation says PMA supply in Australia occurs in waves, and is particularly dangerous because its hallucinogenic potency which is "approximately five times that of mescaline and three times that of MDMA."

In addition to the street name 'Dr Death', users can also be fooled by the drug being sold as 'Pink ecstasy', 'chicken yellow' and 'chicken powder'.