By Danny Shaw BBC home affairs correspondent

When he was home secretary under the last Conservative administration, Michael Howard used to apply the principle that "prison works" to the party's policies on crime.

This Labour government is becoming attached to the idea that "treatment works" in relation to drugs.

The idea underpins their 80-page drug strategy and is based, according to ministers, on sound research.

Indeed, the target to double the number of problem drug users on treatment schemes over the next six years is the only surviving target from the 1998 drug strategy.

Recruitment 'problem'

The problem with current treatment programmes is that that there are not enough of them, so in some areas there are long waiting lists.

For drug addicts leaving prison, there is little aftercare.

And across the UK there is a shortage of trained and qualified drug counsellors.

Cannabis laws are being relaxed

Ministers are investing hundreds of millions of pounds to increase treatment provision - but recruitment may prove to be the toughest obstacle.

There have already been some cases where the money has been available to treat addicts, but the infrastructure and staff haven't been ready.

One key problem is that the people drug agencies and support groups would like to employ are also being wooed as potential nurses, probation staff and social workers.

The pool of public sector workers has its limits.

Better treatment facilities are also central to the new national crack action plan, designed to combat a worrying rise in the use of crack and cocaine among young people - particularly those from African-Caribbean communities.

Heroin on prescription

But many crack users are hooked on other drugs as well; their addiction is part of, and fuels, a chaotic lifestyle which needs to be tackled in a variety of ways. For them, treatment will be a complex affair.

Heroin, however, is in some respects easier to treat.

Many addicts are able to lead fairly normal lives if they are given a steady, clean dose of the drug or its synthetic substitute, methadone.

That is the thinking behind the government's decision to make heroin available on prescription to all those who have a clinical need for it.

It is a bold move, which ministers have played down, possibly for fear of spreading alarm that it is a step on the road to legalisation.

Harder focus

But that sort of development is not on the agenda - in spite of the decision to downgrade cannabis from Class B to C.

That was simply to allow police to focus on harder drugs and give the government's policy more credibility with young people.

A more credible message will be what the government will aim for when it launches a new advertising campaign in the spring.

Do not expect staged images of heroin users dying on the streets, as in previous initiatives.

This campaign may be addressed as much at improving the drugs knowledge and awareness of parents and teachers, as at teenagers.

Central to it will be treatment - and ways of accessing treatment. If treatment fails, so will the government's drugs policy.