Ministers will not be required to seek the advice of scientists when making drug classification policy in future, under new government proposals.

The police reform and social responsibility bill, published last week, contains an amendment to the constitution of the Advisory Council on the Misuse of Drugs (ACMD) that would remove the requirement on the home secretary to appoint at least six scientists to the committee.

A further amendment to the Misuse of Drugs Act 1971 would allow the home secretary to place temporary controls on substances for a year by statutory instrument.

The proposals will be of concern to the many doctors and scientists who have criticised the government's treatment of scientific evidence in the wake of the sacking, last year, of ACMD chairman David Nutt. The then home secretary, Alan Johnson, removed Nutt from the post after the scientist criticised politicians for distorting research evidence and claiming alcohol and tobacco were more harmful than some illegal drugs, including LSD, ecstasy and cannabis.

At present, the ACMD is required to have a membership that includes representatives of medicine, dentistry, veterinary medicine and pharmacy, the pharmaceutical industry, and chemistry. It is also meant to include people with expertise on the social problems connected with the misuse of drugs.

"The government is ill-advised to hack away at science advisory structures," said Evan Harris, former Lib Dem MP and campaigner for evidence-based policy. "The solution to the poor relationship scientists and Home Office ministers have had is for both to follow their codes of practice, not for ministers to seek to abolish science advisers."

Imran Khan, director of the Campaign for Science and Engineering, said: "It's incredible that the government are trying to take us back to the time of 'Minister knows best'. Scrapping the need for expertise on the drugs advice is not only bad science, but it's also terrible politics."

He added that the status of the ACMD was still a raw nerve for the scientific community – six of its members resigned last year in protest after Nutt was sacked. "The Home Office would be hard-pressed to find a worse fight to pick with the science community," he said.

Crime reduction minister James Brokenshire said: "Scientific advice is absolutely critical to the government's approach to drugs and any suggestion that we are moving away from it is absolutely not true.

"Removing the requirement on the home secretary to appoint to the Advisory Council on the Misuse of Drugs at least one person with experience in six specific areas will allow us greater flexibility in the expertise we are able to draw on.

"We want the ACMD to be adapted to best address the challenges posed by the accelerating pace of challenges in the drugs landscape."

After David Nutt was removed, scientists called on the government to guarantee that any advice they offered to help make policy would remain free from political interference. More than 20 academics drafted guidelines that they said "would enhance confidence in the scientific advisory system and help government to secure essential advice".

The guidelines argued that "disagreement with government policy and the public articulation and discussion of relevant evidence and issues by members of advisory committees can not be grounds for criticism or dismissal."

Leonor Sierra of Sense about Science, which helped to publish the independent guidelines, said: "We are rather surprised that instead of improving on the scientific constitution of the advisory council to deal with any shortcomings in the original legislation this bill proposes doing away altogether with the requirement for scientists. Given the recent history, the government really needs to explain how it will maintain objective clarity around evaluation of substances, particularly new substances, in the face of sensationalist or knee-jerk debates."

Harris said the 1971 Misuse of Drugs Act was ahead of its time in embedding expert and scientific advice into policymaking. "In the forty years since then the need for good evidence to inform policy has increased, yet the government seem to want to go back to a pre-scientific era in policy terms."

Earlier this year, the ACMD members who resigned after David Nutt's sacking launched their own independent committee to provide definitive scientific advice on the risks of drugs. The Independent Scientific Committee on Drugs includes scientists, drug-treatment professionals and representatives from the police. It is committed to assess, in public, the evidence on the relative risks and harms of drugs without regard to political sensitivities.