More than three-quarters of MPs believe the UK's drug policies are not working, according to a poll for a respected commission poised to deliver a landmark report assessing the evidence for continued prohibition.

The poll's publication comes ahead of the release of several major reports into the future of UK drug policy that will ensure the debate about reforming the country's laws becomes a key issue for MPs for the rest of the year.

The poll, conducted by ComRes for the UK Drug Policy Commission (UKDPC), found that 77% of MPs believed the UK's current policies were ineffective in tackling the problems caused by illegal drugs.

The poll of 150 MPs, weighted to reflect the composition of the Commons, found no significant difference between coalition and Labour MPs, with only 18% of MPs from coalition parties agreeing that current policies are working.

It also revealed that MPs had deep concerns about how drug policy is formulated. Two-thirds of those polled said a change in how policy was made was needed to tackle the UK's drug problems effectively. More than three-quarters of the MPs said that drug policy needed to draw much more on evidence and research.

"We knew that the public think that drug policy isn't working well enough," said Roger Howard, chief executive of the UKDPC. "Clearly, many MPs now also think the same. Drug policy in the UK has had some good achievements, like keeping HIV rates low among drug users and getting more people into treatment. But it's now clear to many people that we need some fresh thinking."

The UKDPC, an independent body launched in April 2007, aims to provide independent and objective analysis of drug policy. It will be wound up in the autumn, when it will produce a comprehensive report examining the effects of current policy and make recommendations for the future.

But while there is widespread agreement that existing laws are not working, the UKDPC poll suggests there is little consensus on what needs to be done. It found that most MPs would resist a change in the drug laws. According to the poll, only 31% believe that they should consider relaxing the law so that possession of small quantities of controlled drugs would not be treated as a criminal offence.

Confusion about drugs policy has been reflected in ministerial appointments. Last week's reshuffle saw the government appoint its fourth drugs minister – Lord Taylor of Holbeach – in two years.

Drugs experts said the poll highlighted the challenge now facing politicians. "Transform is delighted to see that almost four out of five parliamentarians know that drug policy is failing," said Danny Kushlick of Transform, an anti-prohibition group. "However, given that so few appear to know what to do about it, conducting a review of all options, including decriminalisation and legal regulation, would provide the evidence for parliament to pursue an effective approach."

Growing disquiet among politicians about the UK's drugs laws reflects wider global unease about blanket prohibition. In February, 12 Latin American countries signed a declaration calling for world leaders to explore legal regulation.

Earlier this year Guatemala's Otto Pérez Molina became the first serving Latin American president to push for drug legalisation. "Drug abuse, alcoholism and tobacco should be treated as public health problems, not criminal justice issues," Molina said, writing in the Observer.

The imminent publication of the UKDPC report and one by the Commons home affairs committee suggests a similar debate is now heading for the UK. The British Medical Association is also expected to publish a report on drug dependency.

"UKDPC will look at how we can tackle drug problems and get better value for public money when we publish our report next month on the future of drug policy," Howard pledged.

The last home affairs committee report into drugs, published in 2002, called for a major shakeup of the government's policy, concentrating on education and harm reduction for users, rather than criminal sanctions. "Drugs policy in this country has been failing for decades," David Cameron, who was then a committee member, declared at the time. "Drug abuse has increased massively, the number of drug-related deaths has risen substantially and drug-related crime accounts for up to half of all acquisitive crime. I hope our report will encourage fresh thinking and a new approach."