LONDON (Reuters) - Cannabis will be raised to a class B drug with a maximum five year jail term for users, the government said on Wednesday, rejecting a recommendation from its own drugs advisers to leave the classification unchanged.

Home Secretary Jacqui Smith said the decision had been made because of concern, particularly amongst the public, about the "alarming" use of skunk, a stronger strain of the narcotic which now dominates the market.

"I want it to be clearly understood that this powerful form of cannabis is an illegal and harmful drug," Smith told parliament, vowing the change would be backed by crackdowns on cannabis farms.

"There is a compelling case for us to act now, rather than risk the future health of young people."

Her announcement followed the publication of a report by the independent Advisory Council on the Misuse of Drugs (ACMD) which said there was insufficient evidence to regrade cannabis to the more serious class B.

"After careful scrutiny of the available evidence, the ACMD considers -- based on its harmfulness to individuals and society -- that cannabis should remain a class C substance," said Chairman Michael Rawlins.

Prime Minster Gordon Brown had been widely expected to ignore the advice because of fears over the mental health effects of skunk.

Last month Brown said he wanted to send a strong message that use of the drug was "unacceptable".
Cannabis was downgraded to Class C -- which includes substances such as anabolic steroids -- on the ACMD's advice in January 2004.

That meant possession of the drug was treated largely as a non-arrestable offence.

Under the tighter class B rules, which put cannabis on a par with amphetamines and barbiturates, users face up to five years' jail and suppliers a maximum of 14 years.

Proponents of a tougher drugs policy said its Class C status ignored cannabis's potential health impacts.

Mental health criminal lawyer Grahame Stowe, a partner at law firm Grahame Stowe Bateson, said reclassification of cannabis is long overdue.

"Those of us who work in the criminal and mental health spheres of the legal industry are acutely aware of the danger cannabis poses and the long-term damage it causes," the lawyer, who has 35 years' experience, said in a statement.

"Reclassification is the only way to address this problem and make concrete progress on tackling cannabis use."

The ACMD was asked by Brown shortly after he took office last June to review the drug's classification and it reported to ministers last week.

Going against the council's advice is controversial given it plays a major role in drugs policy, but Brown was also likely come under fire from those who said drugs policy was too soft if he decided to keep the narcotic in Class C.
Wednesday's move was welcomed by police and the Conservative party, although it condemned the government for the original decision to downgrade the drug, saying it had increased the size of the cannabis market.

(Additional reporting by Michael Holden and Katherine Baldwin; Editing by Steve Addison)