Bikers patrol in London and the South East

Clothes Aid, which collects clothes for Great Ormond Street Hospital Children's Charity, has hired a team of bikers to catch the thieves red-handed.

The bikers patrol the streets with cameras looking for bogus collectors.

The firm has so far successfully recovered 28 tonnes of bags from one depot in east London.

Lettitia Prewitt, a biker for Clothes Aid, said: "We come out very early in the morning.

"We survey the area to find out which bags have been left out very early. We sit there with our camera and we can just keep clicking and clicking until we see them collecting six or seven bags.

"We're looking at tonnes and tonnes of clothing per week. This is just the tip of the iceberg. We should be getting one or two a day, as there's about five of their vans out a day, but we are only catching possibly one a week. But yes, it is vast. It's huge."

A Clothes Aid spokesperson said: "People are being advised not to let these people steal their charitable spirit and to carry on donating clothes."

He urged people to contact the charity or the police if they notice anything suspicious.