Bogus collectors are stealing about 50 tonnes of charity collection bags a week, a doorstep collection agency has warned.
The figures from Clothes Aid, which carries out doorstep collections for a number of not-for-profit organisations, show thefts have increased by 30 per cent in the past five months.
It means charities are losing out on about 200 bags of clothing every week - an estimated annual financial loss of up to £3m.
Clothes Aid reported a 30 per cent drop in thefts last year after an awareness campaign run in partnership with the police.
However, a spokesman for the organisation said thefts were back to previous levels. "With knife and gun crime on the rise, the police have higher priorities than catching charity bag thieves," he said.
"I imagine it will just get worse as people look for alternative means of income in this recession."
David Moir, head of policy and public affairs at the Association of Charity Shops, said high textile prices were also causing shops to lose out.
He said agencies were collecting bags on behalf of charities, giving them small payments of between £50 and £100 a tonne, then selling the clothes to foreign rag merchants for a huge profit.
"One organisation is even offering £4 a bag if people deliver directly to its depot," he said. "That kind of loss is a hell of a lot more worrying than bogus collectors and random thieves."