The Trading Standards Institute is warning that just six boroughs in the city had dedicated trading standards officers in December 2001.

It fears the black market will continue to grow unless more officers are taken on.

Tony Northcott, from the institute, told BBC London "this kind of activity will increase" unless they can find some young recruits.

"There will be fewer people to find people who are perpetrating this problem and that means that everyone will lose out," he said.

"The difficulty in London is that the vast majority of trading standards officers, some 45%, are in their 40s.

"And of course as people get older that will increase through to their 50s and there are not enough people coming in as qualified officers in the 20 to 30 age bracket."