An independent committee that advises ministers on drug classification is poised to recommend the controversial downgrading of ecstasy to a class B drug. The Advisory Council on the Misuse of Drugs (ACMD) is expected to call for ecstasy, a drug blamed for the deaths of at least 30 people a year, to be changed from its top-rated class A category when it reports later this month.

The proposal will bring the council into direct conflict with the Home Secretary, Jacqui Smith (below), who is expected to veto any such move, and propel the Government into a row over its treatment of expert bodies charged with advising ministers on key issues. The controversy comes just months after the Home Office ignored ACMD opposition to the decision to move cannabis from class C to class B.

Senior Home Office sources said they "fully expected" the ACMD to call for the relaxation of ecstasy's classification. Professor David Nutt, chairman of the committee, which is reviewing ecstasy at the request of MPs, has suggested it is less dangerous than alcohol or tobacco, and stated that it is "probably too highly classified".

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Downgrading the drug, which is popular with clubbers, to class B would reduce the maximum prison sentence for possession from seven years to five, while the maximum prison sentence for dealers would fall from life in prison to 14 years. It shares its current classification with drugs such as heroin and crack cocaine.

Anti-drug campaigners have attacked any move to downgrade ecstasy. The shadow Home Secretary, Dominic Grieve, said: "Drugs wreck lives and destroy communities. Ecstasy is a drug that is very damaging."

Critics have also called into question the ACMD's fitness to advise ministers. David Raynes, a member of the National Drug Prevention Alliance, said the ACMD should be "an impartial centre of expertise carefully weighing evidence and public good". He added: "Recent behaviour leads me to believe it is being controlled by a few ideologues, pursuing a broadly liberal and pro-drug, legalisation agenda."

Mary Brett, spokesperson for Europe Against Drugs, said: "The present ACMD includes few members who take a definite drug-prevention stance. It is imperative that a committee of this importance needs to be properly balanced."

Professor Andy Parrott, an experton ecstasy, said he was concerned that there were insufficient scientists on the committee. "It is quite an odd committee. It is not very scientific. This issue should not just be about opinions – it should be about the actual effects this drug has on people's brains and bodies. I have conducted years of research into ecstasy and I can tell them that it is not possible to take this drug without being damaged by it."

In a critical report on drugs policy in 2006, MPs on the Science and Technology Select Committee accused the ACMD of a "dereliction of duty" over its failure to alert the Home Office to serious doubts about the system's effectiveness. The MPs also expressed "surprise and disappointment" that the ACMD had never reviewed the evidence for ecstasy's class A status.

A Home Office spokeswoman said the ecstasy review was "hugely unwelcome". She added: "Ecstasy can and does kill unpredictably; there is no such thing as a 'safe dose'. The Government firmly believes that ecstasy should remain a class A drug."