The Home Secretary today said he was "very worried" about new medical evidence linking cannabis consumption with mental health problems.
Charles Clarke's comment came just weeks ahead of an expected announcement on whether he will reverse predecessor David Blunkett's controversial decision to downgrade the drug from class B to class C.
It is the strongest indication yet that he is preparing to restore cannabis to the more serious category, less than a year after reclassification took effect.
Speaking to The Times, Mr Clarke said that Blunkett's decision to downgrade the drug had left people confused about the potential impact of the consumption of cannabis.
Over the Christmas break, the Home Secretary has considered the report of a special advisory group he commissioned to assess the latest medical opinion on the effects of cannabis.
He today declined to discuss the report's contents in detail, but said that he would accept a key recommendation to step up education about the effects of cannabis and its legal status.
And he said it was significant how many supporters of reclassification have changed their minds in the light of new medical evidence.
"I'm very struck by the advocacy of a number of people who have been proposers of the reclassification of cannabis that they were wrong," he told The Times.
"I am also very worried about the most recent medical evidence on mental health. This is a very serious issue."
Asked whether Mr Blunkett's decision to downgrade cannabis had led to confusion, Mr Clarke responded: "Yes. People do not understand the impact of the consumption of cannabis well enough and what the legal consequences of consuming cannabis are."
He promised to take action to reverse the alarming lack of knowledge about the health dangers of cannabis, which has been linked in some studies to schizophrenia and other mental problems.
"Whatever happens after this, let me reveal one recommendation of the advisory committee - which they make very, very strongly - which is a renewed commitment to public education about the potential effects of the consumption of cannabis and the legal status of cannabis," he said.
"That is well made and I will accept it."
Under Mr Blunkett's reclassification, cannabis remained illegal and users could be sentenced to up to two years in jail for possession of the drug and dealers to up to 14.
But police were advised that most cases where people were found in possession of small quantities of cannabis should result in a warning and confiscation of the drug, rather than an arrest. This led to the widespread perception that its use had effectively been decriminalised.
Advocates of reclassification argued that it would allow police to concentrate their attentions on tackling the use of more serious and harmful drugs.
Asked today if the downgrading of cannabis had served any useful purpose, Mr Clarke said: "I think it gives a steer to the citizen on more serious drug consumption."Reuse content