Party members cheered as the result of the vote - 426 in favour of decriminalisation and 375 against - was announced to the party conference in Brighton.
But the controversial decision was a blow to the party leaders, and particularly Alan Beith who, in his first platform appearance as the party's home affairs spokesman, warned against sending a wrong signal to the electorate.
Paddy Ashdown was said to be furious and, in a statement released later, emphasised that decriminalisation would be considered by a Royal Commission on drugs misuse which the conference supported. 'Our manifesto at the next election will contain a commitment to a Royal Commission only, not to the decriminalisation of cannabis,' he said.
Mr Beith said the deadly presence of Ecstasy on the rave circuit showed how easily a bad situation could be made worse: 'I would take a lot of convincing before I would be prepared to take the risk of signalling public approval of what is dangerously described as 'recreational' drug-taking because that signal could so readily increase the use of other drugs.'
But a succession of speakers argued that cannabis was less harmful than alcohol and tobacco, and decriminalising it would enable the police to concentrate their resources on combatting hard drugs. It was not a 'wooly hat and sandals' amendment and would allow cannabis to be licensed and taxed.
Proposing the move, Alan Dean, of Saffron Walden, Essex, said Liberal Democrats would be releasing 'the logjam of thinking on drugs' among political parties. As a father of three teenagers he was concerned that the present approach to drugs had failed.
The debate did not dissolve into an argument over the definitions of decriminalisation and legalisation. But the intention of the vote appeared to be that individual use should be legal, but dealing in the drug should remain outlawed.
Commenting on the vote, the Tory Home Secretary, Michael Howard, said it was wrong to legalise cannabis and wrong to vote for its legalisation. He said the vote showed how 'irresponsible' the Liberal Democrats were.
Conference reports, page 7
Andrew Marr, page 12Reuse content