Cocaine use is now so widespread that everyone in Britain is carrying around traces of the drug – on their banknotes.

A study of cash from around the country has revealed that 99.9 per cent of all banknotes now carry traces of the class A drug, a level only previously seen in cocaine hotspots such as London.

The research, by forensic scientists at the Bristol-based company Mass Spec Analytical, showed that even currency circulating in rural areas is almost always contaminated with the drug.

It comes as figures released by the Government reveal a 70 per cent drop in the amount of cocaine seized by customs officials between 2003 and 2005.

Dr James Carter, who led the research, said that traces of other drugs such as ecstasy, heroin and cannabis, had also been found on banknotes, but at far lower levels because the substances break down more quickly.

"Once cocaine is fixed on to a note it tends not to come off," he said. "The cocaine particles become caught up in the fibres of each banknote."

Particles of the drug were initially dissolved in finger grease and passed to notes by human contact.

Mass Spec Analytical examined more than 1,500 £10 and £20 notes withdrawn from banks in nine separate rural and urban locations. The figures suggest that just three million of the two billion notes in circulation are now drug-free.

Plummeting prices and its image as a celebrity drug have seen cocaine become the fastest growing "recreational" drug among young people. Traditionally associated with high earners, it has become popular among clubbers and even schoolchildren.

A spokesman for Drug Concern, a support group, said the contamination of banknotes reflected a worrying rise in the use of the class A drug.