Drug czar's warning

New alerts were issued today over the use of cannabis in the capital. Ken Livingstone's chief adviser - who used to advocate softer drug laws - said too many people were flouting the law by smoking the drug in public.

And counsellors warned of a dangerous new form of cannabis laced with crack cocaine which could prove lethal.

The warnings come on the first anniversary of the Government's decision to relax the law on cannabis. Since January last year, most users caught in possession have been let off with informal warnings rather than arrested - although the drug remains illegal.

Metropolitan police officers have complained of confrontations with youths who believe they are now entitled to smoke the drug openly.

But Lee Jasper, who advises the Mayor on policing, told a conference at City Hall: "If you see the extent to which cannabis is smoked outside schools, on London Transport, it's unacceptable. I think public use of cannabis, particularly in certain areas, should be subject to some sort of enforcement other than that which is currently used."

Mr Jasper was a leading proponent for decriminalising cannabis. In 2002, he said a relaxation of the laws had been proven to cut the number of street robberies and other crimes, and to have "a huge impact in dealing with class-A drugs, particularly crack cocaine". He claimed a "sensible attitude" had also "freed up tremendous police resources".

Mr Jasper's son Remi was recently arrested in Lambeth with a small bag of cannabis, but was released after officers decided it was for his personal use.

Meanwhile, a charity working with young cannabis users says dealers are lacing the drug with crack cocaine and chemicals to create a dangerous combination. Camila Batmanghelidjh, of Kids Company said: "Weed is being mixed with crack cocaine. It is no longer a natural herb. Cannabis such as skunk is also full of harmful chemicals. It is a very frightening development. The kids know this, but they buy what they can get."

Ms Batmanghelidjh said of the 500 children seen by Kids Company, 400 smoke cannabis daily. Since most are on benefits many turn to crime to fund their habit, which can cost as much as ?70 a week.

She said the increasing strength of the drug has led to a rise in mental health problems among children. "We are seeing a higher prevalence of breakdowns as a result of excessive use, especially if there's a history of schizophrenia in the family," she said. "The drug also causes memory impairment and lack of motivation. Reclassification has sent the signal that it's okay to smoke dope. But in inner-city neighbourhoods we are not talking about a drug that is used occasionally. These children are using it to self-medicate to counter the stress in their lives brought on by sex abuse, trauma, hyperactivity."

There was public confusion when cannabis was downgraded from Class B to Class C on 29 January last year and opinions are still divided about the impact.

Supporters say there are fewer cannabis-smokers clogging up police stations and courts, and young people are no longer gaining criminal records for experimenting with a recreational drug.

But critics say cannabis use has increased while "postcode policing" has left users facing tougher penalties in some areas than others.

It emerged today that police have designated certain streets in London where routine arrests of cannabis users have continued. One in Stockwell is a known haunt for drug dealers. Local police commanders decided that letting cannabis users off with warnings would set back their efforts to curb the trade.

Across the UK, cannabis users are let off with warnings unless there are "aggravating factors" such as possessing the drug near a school or smoking it in public view.

Cannabis possession remains an arrestable offence, punishable by two years in prison. The maximum sentence for dealing has been kept

at 14 years. Under-18s caught with cannabis still face routine arrest.

Met figures reveal a slight drop in the number of cannabis offences. In 2003 - pre-classification - there were 24,535 offences related to trafficking and possession of cannabis. The following year, when the law had changed, that had dropped to 22,315. But arrests were down by a third, and the Home Office estimates that 180,000 hours of police time will be saved this year.

A Met report, based on consultation with senior officers, stated: "The reclassification has sent out a mixed and confusing message to police officers and members of the public."