'This will achieve nothing. If anything it will celebritise the taking of illegal substances. This is purely anecdotal. It's not part of any proper study. It's publicity-seeking TV at its worst.'
A spokesman for the Transform Drug Policy Foundation said the show was no way to explore drug problems.
'There are lots of important issues around drug use in a popular culture,' he said. 'I'm not convinced this is necessarily a good way to explore them.
'From previous attempts, footage of people taking drugs is usually quite dull and probably unenlightening.'
Allen is among a number of celebrities who have been administered drugs and then had their brains scanned for the Drugs Live programme.
Television bosses insisted it would be a 'serious look at drugs' such as cocaine, marijuana and ecstasy.
A Channel 4 source said: 'Anything that's done will have to be done ethically and scientifically. We aim to reflect all points of view.
'This is a serious scientific documentary and we want it to be a balanced project.' The study is being conducted by researchers Professor David Nutt and Dr Robin Carhart Harris, at Imperial College London.
Controversial drugs expert Professor Nutt was sacked in 2009 as chairman of the independent Advisory Council on Misuse of Drugs after claiming alcohol and tobacco were more harmful than LSD, ecstasy and cannabis.
He has also suggested horse-riding is more dangerous than taking ecstasy and said alcohol consumption in Britain would fall by a quarter if Dutch-style cannabis 'coffee shops' were introduced.
Channel 4 chief David Glover said: 'This subject is fraught with controversy and confusion. The aim is to bring new clarity to the facts of illegal drug use.'
Participants in the show will take controlled substances 'under strict medical supervision and in a controlled clinical environment', while their reactions are filmed.
Organisers plan to work alongside the Home Office on the series, which will air in September, and say they will have all the 'relevant approval'.
Allen, who played the Sheriff of Nottingham in the BBC's Robin Hood series, has long been outspoken about his drug use.
Critics fear his participation in the programme will only serve to glamorise illegal substances.
In 2007, he revealed how he used his pop star daughter to sell drugs at Glastonbury Festival when she was younger, saying: 'I didn't see what was wrong with taking little Lily along with me as a sales tool.'
But the actor, who has worked on a series of Channel 4 documentaries before, said he feels he can be misrepresented, as he has never been a big drinker and 'can go for months without taking drugs months and months'.
A Home Office spokesman said: 'Any unlicensed possession of Class A drugs is a criminal offence, unless this is done under authorisation from the Home Office.'
- Daily Mail
