TONY Blair is about to make one of his most controversial decisions since he teamed up with George W Bush for the disastrous invasion of Iraq.

But this time it is nothing to do with smoking out murderous tyrants - and everything to do with smoking hash, gear, weed, ganja, Mary Jane or, more simply, cannabis.

All the signals point to the Prime Minister regretting the decision to downgrade the drug at the start of 2004, which means possession is no longer an arrestable offence.

Mr Blair is desperate to restore the Class B status of cannabis, putting pressure on the police to do more than simply confiscate small amounts and issue a formal warning.

Indeed, his frustration is that the Advisory Council for the Misuse of Drugs, which is looking into fresh evidence of long-term harm, will not report back until December.

The new inquiry follows fears that stronger varieties of cannabis - called "skunk" - are becoming more easily available. And these are more likely to cause long-term mental health problems.

It seems likely there will be a higher classification - and tougher penalities - for these more potent strains than for the student's traditional Moroccan hashish. That means it would fall to police officers on the beat to judge the strength of someone's spliff, to decide whether to arrest or merely issue a caution.

Not surprisingly, Scotland Yard commissioner Sir Ian Blair, Britain's top police officer, has already condemned such a move as "impractical".

The last thing police chiefs want is for officers to be wasting their time dealing with possession offences. It's the reason why cannabis was downgraded in the first place.

They would much sooner concentrate on catching criminals caught up in the use or sale of harder, more dangerous, Class A drugs such as heroin or cocaine.

After all, the cost of acquisitive crime - robberies, burglaries, car break-ins and the like - which can be blamed on addicts runs into millions of pounds a year.

But, leaving aside the effect on police time, where is the logic in tougher penalties for Britain's estimated 3.2 million cannabis users, simply because they smoke a more powerful strain?

Surely the logic points the other way - to the need to take distribution away from the black market so that strength of the drug is regulated and health is better protected?

It is the reason why alcohol is sold in marked bottles and cans displaying the strength of the brew, instead of in blank containers forcing drinkers to buy 'blind'.

When the strength of booze was a lottery, during Prohibition in 1920s America, "moonshine" caused enormous harm. It was why so many of the famous blues singers went blind.

Young people rarely do what the Government tells them. Indeed, research since declassification suggests cannabis-use is no longer rising, precisely because it has lost its mystique.

Bearing this in mind, maybe the best thing Mr Blair could do to kill off the dreaded weed is to stand outside No 10, "skinning up" a huge funny fag. Teenagers would give up immediately.

The Prime Minister could puff away with Chancellor Gordon Brown, giving a whole new meaning to the phrase 'joint initiative'. And if they both wore hooded tops at the same time, even better.

Updated: 09:26 Friday, May 27, 2005