Media playback is unsupported on your device Media caption Nick Clegg: "If you are anti-drugs you should be pro-reform"

Deputy Prime Minister Nick Clegg has backed calls for a royal commission to consider decriminalising illegal drugs, despite opposition from David Cameron.

The PM has rejected the Home Affairs Select Committee's report highlighting Portugal's approach, where people found with drugs are not always prosecuted.

But Mr Clegg told the BBC the government needed to be open-minded and look at alternative approaches.

Mr Cameron said he was "entirely entitled to take a view" on the matter.

Mr Clegg said different politicians of different parties were entitled to take a different view on "how we have another look at how we deal with drugs".

"We can't be complacent, we owe it to the many many children in this country who still get snarled up by drugs, whose education chances are blighted by drugs, whose health is damaged by drugs, we owe it to them to constantly restlessly look for better ways of dealing with the scourge of drugs," he said.

"After all, this is a war, the war on drugs, in which over 2,000 people are losing their lives in Britain every year, in which one in five 11 to 15-year-olds in this country now say they're trying drugs, where young people now are telling us that it's easier to get hold of drugs than it is to get hold of alcohol or tobacco.

Analysis Another day... another coalition disagreement? It's beginning to feel a bit like that. Today we have the the divide over drugs policy. Earlier in the week it was the disagreement over the Communications Bill and monitoring our emails and texts; and before that it was the very public split over the Leveson proposals Those around Mr Clegg insist this is not all part of some carefully planned policy of "differentiation". And yet it does tell us two things. One is the pressure on Mr Clegg to show that life in coalition with the Conservatives has not turned him into some sort of closet Tory; a Cameron-lite figure. And secondly, it tells us how the coalition has now become a much less tightly bound administration. The hope is voters will respect this readiness to speak out. The danger of course is that voters will see this simply see these disagreements as divisions and splits.

"I think those facts alone suggest that, yes of course we should do the good work that we are doing as a coalition government, but we should also be open-minded enough to look at whatever alternative approaches help us help those children more effectively in the future."

Mr Clegg added: "My own view is that we simply cannot be content with the way things are. The worse thing to do is to close your mind off from doing even better."

On his decision to speak on the issue despite the prime minister's opposition Mr Clegg said: "Both the PM and I are relaxed about the idea that this isn't an identikit government.

"The home secretary and indeed the PM are perfectly entitled to say they want the government's present approach to be given a chance to work, and don't want the distraction of a commission."

A royal commission is a public inquiry created by the head of state into a defined subject and overseen by a commissioner who has quasi-judicial powers.

Official figures show that drug use in England and Wales is at its lowest rate under current measurements since 1996.

However, there is concern over the growth and prevalence of "legal highs", some of which have been subsequently banned, amid a recorded rise in deaths linked to their use.

The report from the Home Affairs Select Committee stopped short of supporting a relaxation of legal sanctions for drug use, as suggested by experts at the UK Drug Policy Commission in October, but it did call on ministers to look in detail at the idea.

A recent poll by YouGov found of the 1,805 people surveyed, 60% supported a review of drugs policy by a royal commission and more than half backed a trial of a Portuguese-style decriminalisation of the possession of illegal drugs.

At their party conference last year, the Liberal Democrats voted to establish a panel to consider decriminalising the use of all drugs

Speaking in Brussels, Mr Cameron rejected the call for a royal commission to review drugs policy warning it could "last for years".

He said drug use was falling and the government had a "good record" in tackling drug abuse.

However, he defended Mr Clegg's right to speak out on the issue.

"The deputy prime minister is entirely entitled to take a view for the next election and beyond," he added.

Labour leader Ed Miliband said he was opposed to decriminalisation but the party would make a conclusion after examining the committee's report.

"What would be a problem would be to push into the far future any changes. We need to look now at whether drugs policy is working," he said.

Home Affairs Select Committee chairman Keith Vaz welcomed Mr Clegg's intervention but said he was "disappointed" by the difference of view in the coalition.

"This is the kind of subject that needs to proceed by consensus," he said.

"I hope that Mr Clegg will persuade the prime minister to support him on this issue, so there is one line from the government. We need to get going now on a review of current drugs policy."