Prosecutor Ben Fitzgerald told Southwark crown court that the defendants began the alleged fraud when Barclaycard took on the credit card division of Morgan Stanley in 2008, This is London reports.
Between September 28th and October 8th, he argued, they stole Â£3.5 million in a worldwide spree, including Â£645,000 worth of goods in Britain alone.
Police who raided the flat in question found fake cards and counterfeiting equipment, as well as a type of software linked to the manufacture of the clone payment cards.
Four of the alleged gang - Khi-San Voong, Qiu Yeu, Qiang Xue and Dauy Chung - all deny conspiracy to defraud. A fifth defendant, Cai Caixa, has pleaded guilty. The trial continues.
According to figures recently published by payments association Apacs, losses from card fraud totaled Â£609.9 million in the UK last year.