One of Britain's most senior police officers is to call for all drugs – including heroin and cocaine – to be legalised and urges the Government to declare an end to the "failed" war on illegal narcotics.

Richard Brunstrom, the Chief Constable of North Wales, advocates an end to UK drug policy based on "prohibition". His comments come as the Home Office this week ends the process of gathering expert advice looking at the next 10 years of strategy.

In his radical analysis, which he will present to the North Wales Police Authority today, Mr Brunstrom points out that illegal drugs are now cheaper and more plentiful than ever before.

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The number of users has soared while drug-related crime is rising with narcotics now supporting a worldwide business empire second only in value to oil. "If policy on drugs is in future to be pragmatic not moralistic, driven by ethics not dogma, then the current prohibitionist stance will have to be swept away as both unworkable and immoral, to be replaced with an evidence-based unified system (specifically including tobacco and alcohol) aimed at minimisation of harms to society," he will say.

The demand will not find favour in Downing Street. In his conference speech this year, Gordon Brown signalled an intensification of the existing battle. "We will send out a clear message that drugs are never going to be decriminalised," the Prime Minister told the party.

The Tories also rejected the proposals. David Davis, the shadow Home Secretary, said a more effective move would be the creation of a UK border police force to stop drugs getting into the country as well as expanding rehabilitation centres. He added: "We would put police on the streets to catch and deter drug dealers and we would ensure sufficient prison capacity so they could actually be punished."

Mr Brunstrom, whose championing of speed cameras has made him a hate figure among some motoring groups, also found his suggestion that the war on drugs was unwinnable dismissed as a "counsel of despair" by the Association of Chief Police Officers. "Moving to total legalisation would, in our view, greatly exacerbate the harm to people in this country, not reduce it," an Acpo spokeswoman said.

But the 30-page report, entitled Drugs Policy – a radical look ahead, includes a number of persuasive voices. Today Mr Brunstrom will urge his colleagues to submit the paper to Westminster and the Welsh Assembly. In it, he quotes the findings in March this year of a Royal Society for the Encouragement of Arts commission, which stated that "the law as it stands is not fit for purpose" and argues for the replacement of the 1971 Misuse of Drugs Act with a new Misuse of Substances Act.

That would mean scrapping the ABC system introduced by the home secretary James Callaghan with a new scale that assesses substances, including alcohol and tobacco, in relation to the harm they cause – although he admits banning booze and cigarettes is not likely.

But he notes that figures from the Chief Medical Officer have found that, in Scotland, 13,000 people died from tobacco-related use in 2004 while 2,052 died as a result of alcohol. Illegal drugs, meanwhile, accounted for 356 deaths. The maximum penalty for possessing a class A drug is 14 years in prison while supplying it carries a life term.

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Mr Brunstrom indicates that there is a growing mood for change. He cites the House of Commons Select Committee on Science and Technology, which criticised the Government for failing to switch to an evidence-based policy approach. The report also includes quotes from former home secretary John Reid, admitting "prohibition" doesn't work, and the Olympics minister, Tessa Jowell, conceding "it drives the activity underground". There is also supportive evidence from former Chief Inspector of Prisons Lord Ramsbotham, a retired High Court judge, and Scotland's Drug Tsar, Tom Wood.

As well as hitting the country hard in economic terms – class A drug use in England and Wales costs the country up to £17bn a year, 90 per cent of which is due to crime – there are also a series of socially damaging knock-on effects, he says.

He argues that prohibition has created a crisis in the criminal justice system, destabilised producer countries and undermined human rights worldwide. By pursuing a policy of legalisation and regulation, he concludes, the Government will "dramatically reduce drug-related criminality and will enable significant funds to be transferred from law enforcement to harm reduction and treatment procedures that are known to work."

There was a mixed response from groups that work with users. Danny Kushlick, a director of the charity Transform Drug Policy Foundation, praised Mr Brunstrom for his "great leadership and imagination". But Clare McNeil, a policy officer for Addaction, said talk of legalisation distracted attention from the more important issue of rehabilitation. "We have some sympathy with his views and the reasons and why he believes this but we are not in favour of legalisation," she said.

Nick Clegg, the Liberal Democrat home affairs spokesman, said it was " significant" that a senior police officer had spoken out although he too thought the police chief's views went too far. "Where he is absolutely right is that the Government's drugs policy is failing and failing spectacularly. The refusal of the Government to think radically means we are letting thousands of young boys and girls down.

"I am not persuaded that full legalisation is the way forward but what is necessary is that a more logical and evidence-based approach is needed which is less susceptible to whims of individual home secretaries ... The system does not work as it is."

The Chief Constable's verdict

* British drugs policy has been based upon prohibition for the last several decades – but this system has not worked well. Illegal drugs are in plentiful supply and have become consistently cheaper in real terms over the years.

* The number of drug users has increased dramatically. Drug-related crime has soared equally sharply as a direct consequence of the illegality of some drugs. The vast profits from illegal trading have supported a massive rise in organised crime.

* The ABC classification of drugs is said by the RSA Commission to be indefensible and is described as "crude, ineffective, riddled with anomalies and open to political manipulation". Most importantly, the current ABC system illogically excludes both alcohol and tobacco.

* Mr Brunstrom says: "If policy on drugs is in the future to be pragmatic not moralistic, driven by ethics not dogma, then the current prohibitionist stance will have to be swept away as both unworkable and immoral. Such a strategy leads inevitably to the legalisation and regulation of all drugs."

* The chief constable asserts that current British drugs policy is based upon an unwinnable "war on drugs" enshrined in a flawed understanding of the underlying United Nations conventions, and arising from a wholly outdated and thoroughly repugnant moralistic stance.

* He concludes: "The law is the law. In the meantime, I will continue to enforce it to the best of my ability despite my misgivings about its moral and practical worth."