Crack is a highly addictive form of cocaine

Three-quarters of the world's cocaine supply comes from Colombia, South America.

From there the main export routes are to North America and Europe and according to Matt Hamilton, of the Scottish Drugs Enforcement Agency, there are a number of ways by which cocaine comes into Scotland.

He believes profit is the motivating factor for any attempt to expand crack from its main UK market in England.

Andrew Horne leads one of Scotland's biggest drug projects and he said he had seen evidence of more crack on the streets.

But he has sounded caution and believes there needs to be a sense of proportion about the growing problem.

Heroin remains the biggest drug in Scotland.

Highly addictive

Crack cocaine is known to be highly addictive and is made by reducing cocaine powder into crystals.

It is smoked rather than snorted and is quickly absorbed into the body.

Like cocaine, it gives a general feeling of wellbeing, sharpness and physical strength.

But side effects include feelings of panic, depression and anxiety and large doses can induce paranoia.

In rare cases, overdose can lead to heart failure and death.

Crack's effects are more intense than those of cocaine and the high usually wears off after 15 minutes.

Breathing problems

Regular users can become very restless, suffer insomnia, and some develop paranoid psychosis and respiratory problems.

The crack cocaine capital of the world is still reputed to be New York. The drug took hold there more than a decade ago and is still blighting the city.

But the Home Office is now recognising the problem in the UK and has carried out surveys in a number of English regions.

Research, which was published on Monday, was carried out in South Norwood, Liverpool, Nottingham and Sunderland.

It found that crack cocaine users were four times more likely to shoplift and five times more likely to commit robberies than those not on drugs.

The work, undertaken by Dr Trevor Bennett of Cambridge University and funded by the Home Office, also found that Crack cocaine users spend an average of �308 per week on their drugs.