Fake Liverpool and Manchester United shirts were seized

More forged goods are seized by police in Northern Ireland than by all the other UK forces put together.

The clothing company, which did not want to be named, is working with police in an attempt to tackle the problem.

The business is estimated to be worth about �135m a year to the criminals - or about �80 per head of population.

Much of it is controlled by paramilitary groups, and typical forged goods are clothes, CDs, DVDs, software, car parts, tools, footwear and pharmaceuticals.

The counterfeiters also offer door-to-door sales, using taxi drivers who are prepared to bring merchandise directly to the door.

Trading conditions are difficult because some people have decided that they prefer to pay a lower price in exchange for counterfeit goods Mike Roylance Adidas

Raids on traders suspected of selling counterfeit goods are a regular occurrence, but detective superintendent Andy Sproule said one of the problems in trying to stamp out the business is that the rewards are high, and the risks relatively low.

"The penalty for being caught in possession of a suitcase full of CDs or DVDs is much less than for being caught with a suitcase full of cannabis, for example, but the profits are much the same," he said.

"From a public perception, they see criminals as providing a service, offering goods at a cheaper price.

"But those goods are sub-standard, frequently defective, and they're lining the pockets of organised criminals."

Some top brand names employ their own specialists specifically to deal with the problem.

Mike Roylance, a brand protection manager with Adidas, said counterfeiting was huge business in Northern Ireland, but that it would not stop his firm marketing their products in the province.

"Most of it is pretty low-quality stuff which is either made in Northern Ireland or brought in from the south," he said.

"There is no doubt that it is a big problem, certainly much bigger than in any other part of the UK.

"But we are not going to let that put us off.

"Trading conditions are difficult because some people have decided that they prefer to pay a lower price in exchange for counterfeit goods, but we are determined to continue selling our goods in the Northern Ireland market."