Plans for tougher penalties for cannabis possession were unravelling within hours of being announced yesterday by the Home Secretary.

Jacqui Smith outlined a tiered approach of stiffer sanctions for adult offenders repeatedly caught with cannabis after it is upgraded to a Class B drug in January.

Ms Smith said that she was backing a “three strikes and out” system of dealing with adult offenders, starting with a warning from police, increasing to an £80 fine for a second offence and arrest for the third time that a user was found with cannabis.

The approach was undermined immediately, however, when the Home Office said that warnings for a first offence would not be placed on the police national computer. This would make it difficult for police to check whether someone found with the drug was a first or second-time offender, particularly if the cannabis user was caught in a different police force area from where he or she lived.

The drug was downgraded to Class C in 2004 by David Blunkett, the Home Secretary at the time, but Gordon Brown has made clear that he wants the decision reversed, despite a recommendation by the official Advisory Council on the Misuse of Drugs that the present classification should not be changed.

Ms Smith, who admitted last year that she had tried cannabis while at university, added: “We need to act now to protect future generations.”

Tim Hollis, the Chief Constable of Humberside, who speaks on drugs for the Association of Chief Police Officers, has promised tougher action against drug users.

Danny Kushlick, from the Transform Drug Policy Foundation, said that the move was “populist posturing”. He said: “Escalating penalties for possession only serve to further marginalise and criminalise millions of otherwise law-abiding people.”

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