The government is to launch a £1 million publicity campaign to send out the message that cannabis will remain an illegal substance despite next week's reclassification.

David Davis, shadow home secretary, said: "The home secretary has said that if the reclassification of cannabis does not work, he is not prepared to consider reversing the policy. This is an unbelievably arrogant statement to make.

"If there is a significant increase in cannabis use, especially amongst young people, will he stick to the policy?

"If there is a significant increase in hard drug use, will David Blunkett admit he was wrong?

"If there is further evidence showing the health risks from cannabis use, why won't he reconsider the policy?

"If a significant number of people suffer serious side-effects from cannabis use, why won't he contemplate changing his policy?

"If there is an increase in drug related crime as a result of cannabis use, why won't he change his mind?

"The reclassification of cannabis should be judged on its outcomes. This Ggvernment has become too arrogant to know when to admit it is wrong. For David Blunkett to state categorically that he will not reverse the policy, regardless of the consequences, is absurd. We need a grown up debate on drugs, but David Blunkett won't have one."

Forum Response: SANE

Marjorie Wallace, chief executive of mental health charity SANE, told ePolitix.com: "For years the government failed to warn either schools or the public, particularly the most vulnerable young people, about the mounting evidence of the damage cannabis can inflict on still developing brains.

"It is now producing a campaign too late to have any chance of reversing the message that the substance is safe. A million leaflets will be like flowers on the graves of the significant few for whom early exposure to cannabis will mean developing an illness like schizophrenia, suffering hallucinations, paranoia and descent into mental disintegration.

"The government has produced an entirely split policy. While reinforcing the criminal aspects of cannabis, by lowering its classification it is giving out the message that it is not a serious substance. No amount of information, which most schoolchildren won't read or heed, will counter the implicit condoning of the drug for recreational use."

Forum Response: Depression Alliance

Jim Thomson, chief executive of Depression Alliance, told ePolitix.com: "The legal status of cannabis does not appear to make much difference to those who regularly use it.

"However, education around the health risks associated with this drug should be promoted at every available opportunity especially in light of its recent reclassification and the associated £1 million advertising campaign budget.

"This would perhaps go someway towards allaying the fears of the BMA."

Forum Response: The Salvation Army

Jonathan Lomax, public affairs officer at The Salvation Army, told ePolitix.com: "Ever since it was announced that cannabis was to be downgraded to a category C drug The Salvation Army has spoken out publicly, and to ministers, to voice its strong concerns.

"The Salvation Army believes that the reclassification of cannabis is sending very mixed messages to impressionable young people - and just at the time when more and more research is showing that cannabis can cause substantial psychological and physical harm.

"Smoking Cannabis has been implicated in causing added brain damage in people who have nutritional deficiencies, particularly because of a lack of vitamin B.

"This kind of deficiency is prevalent among those with extremely poor diets, either because people are living on low incomes or because of a lack of knowledge about how to eat healthily. The Salvation Army is concerned that any increase in cannabis use could have a disproportionally greater impact on those with low incomes."