Pub staff are being targeted by international criminals using bribes and threats to force them to "clone" customers' credit cards.
The Association for Payment Clearing Services (APACS) has discovered barstaff helping counterfeiters by "skimming" cards using electronic readers.
APACS spokeswoman Melanie Hubbard said it was important not to underestimate the danger posed to staff by the card thieves.
"Criminals routinely use bribes and coercion to persuade pub staff to skim cards," she said. "The message we're trying to get across is that these are dangerous, organised criminals - not the sort of people you want to get involved with at all."
APACS has joined the police in targeting barstaff with a new campaign to raise awareness of the problem.
The pub trade lost £3m last year because of criminals paying with counterfeit cards.
However, APACS believes far more is lost through barstaff helping counterfeiters. The data collected from the electronic readers is used by criminals to create a copy of the card without the customer realising they have done it.
The crime syndicates behind the rackets use the profits from card fraud to fund other crime, including the global traffic in drugs and counterfeit goods.
A specialist police unit has been set up to target these criminals.
Home Office crime reduction minister John Denham said: "The new unit will enable this kind of fraud to be tackled more effectively. It is important business plays its part by taking responsibility for ensuring their own systems are not vulnerable to fraud."
APACS offers a £50 reward to staff who spot any fake cards, rising to £500 for information that leads to the conviction of anyone involved in counterfeiting.