Opposition is growing to the government's decision to reclassify cannabis as a class B drug.
Danny Kushlick of charitable thinktank Transform Drug Policy Foundation says the government's decision to reverse its January 2004 downgrading of cannabis to class C reflects the "political travesty" of current drug policy.
Home secretary Jacqui Smith told the Commons yesterday she was not willing to "wait and see" the extent of the drug's damage to individuals and society.
Mr Kushlick told politics.co.uk her decision proved the government flew in the face of scientific advice and that it was only paying "lip service" to experts in the field of drug prevention.
"For decades now, drug policy has been treated by senior politicians as political Viagra," he said.
"It's a way of showing how tough and hard they are and has been in no way about the developments that have affected public policy. Cameron and Brown have been spurring each other on to ever more facile prohibitionist nonsense and this is the result."
Mr Kushlick's thinktank Transform advocates legalisation of all drugs and is seeking a complete review of the entire Misuse of Drugs Act.
Other, more moderate, groups have joined Transform in opposing the government's cannabis U-turn.
Mental health charity Rethink pointed out the proportion of young people using cannabis has fallen since reclassification in January 2004.
It believes a "full-scale public education campaign" is needed on the issue instead of "wasting time and money" on reclassification.
Drug charity DrugScope's chief executive Martin Barnes said the clearest message given out by the reclassification was that "drugs policy can be driven as much by political considerations, media headlines and scare stories as by the evidence".
Even police officers appear uneasy at the decision. Police Federation chairman Jan Berry said: "We told the government that it was sending a confusing message when they decided to reclassify cannabis four years ago.
"They must now make sure they do not compound this confusion by their decision to re-classify it to a class B."
The Liberal Democrats have criticised the government for ignoring the advice of the Advisory Council on the Misuse of Drugs.
But the majority of MPs belong to parties which back the reclassification to class B, as shadow home secretary David Davis made clear yesterday.
He told the Commons the government's move was a "long-awaited U-turn" and said the move highlighted its "historically lax approach to drugs".