The United Nations Office on Drugs and Crime said the UK is Europe's largest cocaine market - with more than one million regular users.

But its report revealed the quality of the Class A drug has declined dramatically in recent years.

Some seizures by police revealed substances being passed off as cocaine that were only 5 per cent pure.

The World Drug Report 2009 revealed that cocaine use increased dramatically in the UK from the mid-90s, but remained stable over the last two years.

Data given to the UN by the UK's Serious Organised Crime Agency (Soca) shows wholesale prices have risen to record levels.

The cost of a kilogram of cocaine has increased by 50 per cent from £30,000 to £45,000 since 2007.

There are estimated to be 860,000 cocaine users in England and Wales and around 140,000 in Northern Ireland and Scotland combined.