Gordon Brown will press ahead with toughening up cannabis laws despite claims there is no scientific basis for a change, it was revealed today.
The Government is to reject recommendations from a high-powered group of advisers who believe it should stay a "soft" drug.
The Prime Minister is believed to regard the move as crucial for sending a clear message to young people that cannabis is harmful and linked to serious crime.
A final report from the Advisory Council on the Misuse of Drugs (ACMD) was delivered to the Home Office today - although the Government's response will not be announced until next week at the earliest.
The experts - including doctors, police, judges and drug counsellors - are understood have concluded that cannabis should remain in the Class C category.
However, Whitehall sources indicated that Mr Brown was determined to push through reclassification to Class B.
Going against the ACMD's decision could spark a massive row and trigger resignations from the committee, which plays a crucial role in setting Britain's drug policy.
Liberal Democrat home affairs spokesman Chris Huhne demanded that the panel's recommendations be published.
"The Government must stop playing politics and publish this advice as soon as possible," he said.
"There should be nothing secret about the scientific advice being given to ministers on this important issue."
Shadow home secretary David Davis said: "This would not come a moment too soon.
"While Gordon Brown has dithered over this, over 24,000 people - including nearly 9,000 under 18s - are estimated to have been forced to seek treatment for cannabis misuse in England alone.
"One cannot underestimate the real harm cannabis can do to a young person.
"The demotivating and debilitating effect cannabis can have at the most crucial stage in a young person's development can seriously harm their life chances."
A spokesman for Mr Brown said the results of the ACMD inquiry would not be published this week.
"We do have a statutory duty to take into account the advisory committee's advice so there will need to be proper consideration of what they have to say once we've seen the report in full," he said.
Official data revealed earlier this year showed abuse of highly-potent "skunk" cannabis has escalated in the past six years with the drug now dominating the cannabis market in England and Wales.
The powerful strain accounted for just 15% of seized cannabis in 2002 but now makes up between 70% and 80%, initial results of a Home Office-funded project showed.
Home Secretary Jacqui Smith has insisted she still has an open mind about whether cannabis should be reclassified, following reports that ministers would ignore the ACMD's advice if they recommended keeping the drug in Class C.
Its downgrading from Class B in 2004 made possession of the drug a largely non-arrestable offence.
A Home Office spokesman said: "We have today received full advice on cannabis classification from the independent ACMD.
"We are grateful for its detailed report and will now consider it carefully alongside other representations before making a decision on the appropriate classification for cannabis.
"Our message has always been that cannabis is an illegal and harmful drug that should not be taken.
"While evidence shows that cannabis use is falling across all age ranges, we are concerned about stronger strains of the drug.
"That is why we asked the ACMD to undertake a review of cannabis classification."
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