The Government could make a dramatic U-turn on cannabis and raise its classification from Class C to Class B, only three years after it was downgraded.

The Home Office today confirmed it had asked its Advisory Council on the Misuse of Drugs (ACMD) to carry out a review in to whether there is a need to reclassify the drug "given the increasing strength of some cannabis strains" and their potential health impacts.

The review, commissioned by Jacqui Smith, the Home Secretary, was announced by Gordon Brown today.

If the drug is reclassified, reflecting its perceived increased health risks, it would raise maximum penalties for those caught in possession from two years in prison up to five.

It would also mark a significant turnaround by the Government. In 2004 the then-Home Secretary David Blunkett took the reverse decision to downgrade it from Class B to Class C. This was mainly perceived to have been taken because the drug's casual use was so widespread that it was considered impossible to effectively police, so forces' priorities were to be given to other substances.

Speaking at Prime Minister's Questions today in the House of Commons, however, Mr Brown said that Ms Smith would publish a consultation document next week announcing a review of drugs strategy, including the reclassification of cannabis.

"She will be asking the public to comment on new ways in which we can improve drugs education in the country, give support to people undergoing treatment ... and give support for communities who want to chase out drug dealers from their communities," he said.

"As part of the consultation - and the Cabinet discussed this yesterday - the Home Secretary will also consult on whether it is now right that cannabis should be moved from Class C to Class B."

Later, Vernon Coaker, the Government's Minister for Drugs, told Times Online that the review had been prompted by specific public concern at the health effects of the drug.

"We know that cannabis use overall has fallen, but obviously the concern has been raised particularly with regard to the link between skunk and mental health problems such as psychosis," he said.

"Given that that has been raised with us from a number of sources it is only right that we look at it to see whether we do need to reclassify.

"We can't pre-empt the results of the review, and we will obviously take its conclusions into account. But when I go to different meetings in different parts of the country it is raised with me."

Making cannabis a Class B drug would put it on a par with drugs like barbiturates and amphetamines, and would reflect increasing health concerns associated with it, including increasing worries about the rising number of cases of psychosis.

In line with those concerns, an earlier review was commissioned in March 2005 which acknowledged the health risks, but recommended that the classification remained the same.

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