The government's policy on cannabis has been condemned as "confused" because new legislation means possession could lead to arrest.

Under the new Criminal Justice Bill, to be debated by MPs this week, any individuals caught with any Class C drugs could be arrested.

Home Secretary David Blunkett downgraded cannabis from Class B to C in order to allow greater focus on Class A drugs such as heroin and cocaine.

That meant it remained illegal, but possession of small amounts would no longer be considered an arrestable offence.

This about-face makes a mockery of reclassification

Roger Howard Drugscope

The Liberal Democrats and a leading drugs charity have reacted with anger to the new bill, which they say sends out a mixed message.

The Bill also proposes that the maximum penalty for trafficking a Class C drug will rise from five years' imprisonment to 14 years.

Liberal Democrat home affairs spokesman Simon Hughes said his party would challenge the bill.

He said: "Possession of Class C drugs should not be an arrestable offence.

'Muddle'

"The government should be using the bill to send a clear message that the punishment will fit the severity of the offence and the class of drug involved.

"Ministers are in danger of creating a muddle."

Roger Howard, chief executive for the drugs charity DrugScope, said: "This about-face makes a mockery of reclassification.

"Instead of focusing on Class A drugs, saving police time and producing a more logical drugs policy, the small print of this bill means that the law will be more severe and more confused than ever."

In the majority of cases, however, officers will issue a warning and seize the drugs

Home Office

Labour MP for Cardiff Central Jon Owen Jones, who last year tabled a bill to legalise cannabis, said: "It is a very regrettable and difficult to understand decision.

"The government seems to have one foot forward and another foot back."

Home Office notes explaining the provisions of the bill read: "This change in the law would mean that police would retain their power of arrest for possession of cannabis after the proposed reclassification of the drug from Class B to Class C."

A Home Office spokeswoman denied there was any confusion.

She said the Association of Chief Police Officers would be bringing out a guide on the new laws, adding: "It is critical that the police retain the power of arrest to deal with cannabis possession linked to aggravated behaviour that threatens public disorder.

"In the majority of cases, however, officers will issue a warning and seize the drugs."