A trader fears looters going through shop refuse sacks could be trying to steal sensitive information.

Tim White, manager of Computer Assistance, in Cowley Road, Oxford, was first alerted to what was going on when the city council found one of the shop's orange trade refuse bags - which had been left out for collection - ripped open in a nearby field.

He said it had happened several times since.

He said: "There's obviously lots of paperwork to do with running a computer shop, but we've been very careful that no personal information about customers' computers is put in the bags.

"But if there are companies out there that maybe aren't aware their bags are being looked through, it could be quite serious."

Carol Benney, owner of The Gameskeeper Store, said they had had boxes and bags ripped open, leaving rubbish scattered in the street.

She said: "I think they're just looking for anything that's of any value to them.

"I don't put personal material in the refuse, either my personal bins or the shop bins, because that's the sort of thing that leads to trouble. But not everyone is so careful."

Jamie Chivers, who works at Cycloanyalysts, said: "Every time I see them, they are looking for food, digging through people's rubbish.

"We don't put any sensitive information in the bags, we shred it all, so it's just cardboard and packaging.

"It's not very nice though, there's rubbish all over the street."

Corporate identity theft - which costs UK industry more than £50m a year - was reported to be on the increase last year.

Fraudsters can change the names of the registered office and directors of a company - effectively stealing the company's identity - simply by lodging forged forms at Companies House. The company's assets could be stolen and bank accounts emptied.

Fraudsters who have stolen a firm's identity could also then trade on its creditworthiness.

They can order goods and services on credit, leaving the company to be sued when they fail to pay up.