Former defence secretary described war on drugs as 'nothing short of a disaster' and called on government to look at other options

Ed Miliband, the Labour leader, said today that the legalisation of drugs would send out "the wrong message" to young people as he distanced himself from a Labour backbencher's calls for a "grown-up debate" on the issue.

Bob Ainsworth, the MP for Coventry North East, who previously served as a drugs minister in the Home Office and as defence secretary, has claimed that the war on drugs has been "nothing short of a disaster" and that it was time to study other options, including decriminalising possession of drugs and legally regulating their production and supply.

His comments were met with dismay by the party leadership, while fellow backbencher John Mann claimed that Ainsworth "doesn't know what he's talking about".

A spokeswoman for Miliband made clear that Ainsworth's comments did not have the blessing of the leadership or the wider party. She said: "These are not the views of Ed Miliband, the Labour party or the wider British public."

A party source described the legalisation proposal as "extremely irresponsible", adding: "I don't know what he was thinking."

Miliband underlined the fact that Ainsworth's views were at odds with his own as he campaigned in Oldham ahead of next month's byelection.

The Labour leader told Sky News: "I am all in favour of fresh thinking on drugs. I don't agree with him on decriminalisation of drugs — I worry about the effects on young people, the message that we would be sending out.

"I have great respect for Bob as a person. On this one I don't agree with him but he is absolutely entitled to his view and he has the freedom to say things as he sees fit."

Mann, who carried out an inquiry into hard drug use in his Bassetlaw constituency while Ainsworth was drugs minister, said: "He didn't know what he was talking about when I met him with my constituents during my heroin inquiry and he doesn't know what he's talking about now."

Ainsworth, who claimed that his departure from the frontbenches now allowed him to express his "long-held view" on drugs policy, is due to lay out his case later today at a debate in Westminster Hall.

He said his ministerial stint in the Home Office made him see that prohibition failed to reduce the harm that drugs cause in the UK, while his time as defence secretary with specific responsibilities in Afghanistan, "showed to me that the war on drugs creates the very conditions that perpetuate the illegal trade, while undermining international development and security".

He called on those on all sides of the debate to support "an independent, evidence-based review, exploring all policy options, including further resourcing the war on drugs, decriminalising the possession of drugs, and legally regulating their production and supply".

His call for a review was backed by former Conservative party deputy leader Peter Lilley, who said that it was time "for all politicians to stop using the issue as a political football".

"I have long advocated breaking the link between soft and hard drugs – by legalising cannabis while continuing to prohibit hard drugs," said Lilley. "But I support Bob Ainsworth's sensible call for a proper, evidence-based review, comparing the pros and cons of the current prohibitionist approach with all the alternatives, including wider decriminalisation and legal regulation."

Ainsworth cited the legalisation of alcohol in the United States after 13 years of prohibition to argue that after 50 years of global drug prohibition it was time for a "genuine and grown-up debate" about alternatives to prohibition, which he said had "failed to protect us".

"Leaving the drugs market in the hands of criminals causes huge and unnecessary harms to individuals, communities and entire countries, with the poor the hardest hit," he said.

"We spend billions of pounds without preventing the wide availability of drugs. It is time to replace our failed war on drugs with a strict system of legal regulation, to make the world a safer, healthier place, especially for our children. We must take the trade away from organised criminals and hand it to the control of doctors and pharmacists."

The backbencher criticised the government's new drugs strategy, which aims to shift the focus from reducing the harm caused by drugs to recovery as the most effective route out of dependency. "It is described by the home secretary as fundamentally different to what has gone before; it is not," he said.

"To the extent that it is different, it is potentially harmful because it retreats from the principle of harm reduction, which has been one of the main reasons for the reduction in acquisitive crime in recent years."

Ainsworth suggested one way to review the policy would be to conduct an impact assessment of the Misuse of Drugs Act in line with a home affairs select committee recommendation made in 2002 for the government (then Labour) to explore alternatives to prohibition, including legal regulation.

The report by the committee, of which David Cameron was a member at the time, did not support legalisation and regulation in its conclusion at the time, but added that drugs policy should "not be set in stone".

However, one of its recommendations did urge the government to initiate a discussion within the Commission on Narcotic Drugs of alternative ways – including the possibility of legalisation and regulation – to tackle the global drugs dilemma.

James Brokenshire, the crime prevention minister, said: "Drugs are harmful and ruin lives – legalisation is not the answer. Decriminalisation is a simplistic solution that fails to recognise the complexity of the problem and ignores the serious harm drug taking poses to the individual.

"Legalisation fails to address the reasons people misuse drugs in the first place or the misery, cost and lost opportunities that dependence causes individuals, their families and the wider community."

Caroline Chatwin, a drugs policy expert at the University of Kent, said that while it was important for people such as Ainsworth to publicise their support for changes to British drug policy, "it remains regrettable that this public support is unable to be offered by those in a current frontline position".

She added: "Ainsworth states that he is only able to express these views now that he no longer occupies a front line position and Cameron seems to have abandoned his own relatively liberal standpoint on this issue now that he is prime minister. While this suppression of the opinion of those in power continues to be the case, Britain will not be able to participate in an open and honest debate on this subject and will not be able to effect a much needed evidence-based policy."