Mr Iddon was the third Labour backbencher to defy his party line and join the Independent on Sunday's campaign for the decriminalisation of cannabis last year and, following the call by Lord Bingham, the Lord Chief Justice, for a national debate on the issue, he took his concerns to the Home Office prisons' minister, George Howarth.
"A number of people in Parliament, including Paul Flynn and myself, have been very concerned about these priorities in the community in general and I am very pleased to see that Mr Howarth now plans to take action on the treatment of prisoners," he said.
Last week the Review of the Prison Service Drug Strategy reported that the introduction of random mandatory drug tests (RMDT) had resulted in a fall in cannabis use but had notmarkedly affected the use of more harmful opiates. In the light of these findings the "drug tsar", Keith Hellawell, plans to concentrate resources on controlling use of Class A drugs among prisoners.
"We have been suggesting for some months that we take the pressure off cannabis and stick it on heroin and cocaine," said Mr Iddon, a former science academic. "If we concentrate in that area we could spend a lot more on tackling those drugs that do more harm. We could introduce more sniffer dogs and detect the supplies that are still coming in, in a small number of cases, through the back door."
The government report has called for "governors to discriminate effectively within the disciplinary system between more and less harmful drug-related activity, so that the pattern of punishment, and response by way of treatment and support, more closely follows that pattern in the community at large".
Aside from the greater risk to prisoners' health from hard-drugs use, research by the National Association of Probation Officers has shown that half of all property theft is carried out by opiate users.
Suggestions that RMDT may have persuaded prisoners to switch en masse to harder drugs have also been undermined by the findings of the review. While it is true that opiates are not so easily detected because they do not stay in the blood as long as cannabis, the National Addiction Centre's research shows that cannabis positivity rates have fallen whether the opiate status of the prisoner is positive or negative.
"There is no good evidence of substantial individual shifting from cannabis to opiate use to an extent that impacts on overall levels of opiate positivity," the centre's report states.
This backs up Mr Iddon's contention that cannabis users in any environment are unlikely to fall into hard-drug use unless they already have the kind of psychological make-up that would lead them to Class A substances in any case. "The vast majority of people who smoke cannabis do not proceed to other drugs," he insists.Reuse content