David Cameron has firmly rejected Deputy Prime Minister Nick Clegg's call for a Royal Commission to rethink drug laws and ruled out the decriminalisation of any illegal narcotics.
The Liberal Democrat leader dramatically signalled his split with the Prime Minister on the controversial issue by declaring that Britain was losing the war on drugs and a new approach was needed.
But Mr Cameron said the coalition Government had already taken necessary action to change drug policy, and there was evidence that this was bearing fruit in terms of reduced levels of abuse.
He said that Mr Clegg was "entirely entitled" to advocate further change, but made clear that this was only in the context of the Lib Dem manifesto for the next general election, not the policies of the coalition administration.
In an interview with the The Sun, Mr Clegg said that the Prime Minister had missed an opportunity by ruling out a Royal Commission on drugs policy when it was recommended in a report by the influential House of Commons Home Affairs Committee earlier this week.
"If you were waging any other war where you have 2,000 fatalities a year, your enemies are making billions in profit, constantly throwing new weapons at you and targeting more young people, you'd have to say you are losing and it's time to do something different," said the Lib Dem leader. "I'm anti-drugs - it's for that reason I'm pro-reform."
Mr Clegg insisted he is not in favour of full legalisation of drugs but thinks targeting dealers and traffickers, while decriminalising possession, might be a solution. He told The Sun he will include a "clear commitment" to a Royal Commission on drugs in his party's 2015 manifesto.
The Lib Dem leader has ordered Home Office minister Jeremy Browne to compile a report on liberal approaches to drugs across the world which have worked, including in Portugal, Amsterdam, Latin America and several US states.
But Mr Cameron told a press conference in Brussels: "Of course the Deputy Prime Minister is entirely entitled to take a view for the next election and beyond for his manifesto, wanting to go further, wanting a Royal Commission. I personally don't support a Royal Commission. In my view there's always a danger, as someone said, that they can take minutes and last for years."
Mr Cameron stressed that the coalition has already taken action to correct failings in the way the drug problem was dealt with in the past, saying: "We needed a much greater emphasis on treatment. We needed a much greater emphasis on getting people off drugs and able to lead drug-free lives. We needed a much better emphasis on education and effective education about the dangers of drug abuse. We need much more action on drugs in prisons and making sure people can get treatment for drugs in prison to continue the programmes they have had out in the community."