A "suppressed" Government report shows that locking up drug user is nonsensical and the case for reform is overwhelming, according to a Home Office minister.

But Downing Street immediately moved to slap down calls for drugs to be decriminalised as "reckless" and insisted it will not happen.

The coalition Government row broke out after a Home Office study was published that showed treating drug possession as a health problem rather than a criminal matter has no impact on levels of substance misuse.

Drug use is not affected by the "toughness" of a country's enforcement on possession of substances, it found.

Crime prevention minister Norman Baker said continuing the current approach to drugs was no longer tenable.

He told BBC Radio 4's Today programme: "For me the evidence is very clear. If you see a tree, it's a tree."

He added: "I think the evidence personally is so overwhelming that the present status quo is not tenable."

The Liberal Democrat called for dissuasion commissions to be looked into, which would divert people arrested over drugs from the criminal system into the health service.

He pointed to evidence from Portugal, insisting that decriminalisation combined with a tough rehabilitation regime had not led to a significant increase in drug use.

 Mr Baker added: "The reality is that this report has been sitting around for several months. I've been trying to get it out and I'm afraid that I believe that my my coalition colleagues who commissioned the report jointly don't like the independent conclusions it's reached.

"It was suppressed, not by Theresa May, it was suppressed by the Conservatives and the reality is that it has got some inconvenient truths in it."

"What we need to do is recognise that locking somebody up in prison for a matter of weeks because they happen to possess a Class B or a Class C drug is a nonsensical approach. It doesn't change their attitude."

Mr Baker compared drug users to speeding drivers, claiming repeat offenders only stopped breaking the speed limit once they were sent on awareness courses not because of fines.

The Lib Dem said he wanted to "get tough" on drug dealers and organised crime gangs.

"If we can spend more police time chasing those people and fewer dealing with users, that's got to be a good solution. I want to reduce that amount of drugs in our country."

The Deputy Prime Minister earlier this year pledged to abolish prison sentences for the possession of drugs for personal use - including Class A substances like heroin and cocaine.

Mr Clegg has challenged David Cameron to look at issues such as decriminalisation or legalisation of drugs, despite the Prime Minister previously rejecting calls for a Royal Commission to consider the contentious issue.

Number 10 said there was "no chance" that "reckless" calls for decriminalisation would be entertained.

"This report provides no support whatsoever for the Lib Dem's policy of decriminalisation. In fact, it clearly states that it would be inappropriate to draw those kind of conclusions," they said.

"The Lib Dem policy would see drug dealers getting off scot-free and send an incredibly dangerous message to young people about the risks of taking drugs.

"As the report makes very clear, the Government's approach already provides a good balance between enforcement and treatment, drug use is plummeting as a result and there is simply no chance that we will entertain such a reckless change of course ."

In an international comparators study, the Home Office looked at different approaches to drugs policy and treatment in a number of countries, including some that have harsh criminal sanctions for users and some that have effectively decriminalised possession of drugs.

The study found no evidence that levels of drug use were affected by how "tough" or "soft" a government's response is, suggesting criminal sanctions have little impact.

The report also found positive health outcomes in Portugal, where possession of drugs is treated as a health matter rather a criminal issue, and no increase in use.

Worse health outcomes were found in the Czech Republic after drug possession was criminalised, while no evidence of lower use was discovered.

A Home Office spokesman said: "This Government has absolutely no intention of decriminalising drugs. Our drugs strategy is working and there is a long-term downward trend in drug misuse in the UK.

"It is right that we look at drugs policies in other countries and today's report summarises a number of these international approaches."

A separate report calls for a blanket ban on supply of so-called legal highs.

Currently, when a legal high is outlawed, illegal-drug chemists are getting around the law by tweaking the chemical compound and creating a new substance.

Mr Clegg said the report should come as a wake up call to the other parties that the current system was failing.

"This war on drugs is not working. We have got to get away from this facile view that just talking tough solves this problem. It is betrayal of those families of those 2,000 people dying every year in our country," he said on his weekly LBC radio phone-in.

"The evidence shows that a smarter approach where you deal with addicts as people who need treatment so they don't remain hooked on the stuff that is being pushed at them by criminals.

"That actually frees up resources that allows you to go after the pushers and the criminal gangs and the 'Mister Bigs' who should be behind bars.

"I cannot understand why on earth we as a society are putting a thousand people behind bars every year who have only been found to possess drugs for personal use. They have done nothing else wrong."

Mr Clegg accused the Conservatives of a "totally misplaced, outdated, backward-looking view" of the issue.

"The report this morning, pushed by me and the Liberal Democrats against resistance from the Conservatives, is the first time in a generation that a Government-commissioned report has shown the evidence that the way we are doing things doesn't make sense," he said.