The UK's Office of Fair Trading (OFT) is considering whether to take action over an exclusive deal between the London 2012 Olympics and Paralympic organisers and Visa which will prevent fans using other cards to buy tickets.
The deal means that UK cardholders will not be able to pay by card for tickets for the London 2012 Olympic and Paralympic Games, or withdraw cash at any Games sites, unless they have a card which runs on the Visa payment system.
Although Visa has had similar agreements in place for every Olympics since 1988, the London deal has attracted the attention of regulators.
In a statement responding to a request for comment, the Office of Fair Trading says: "The OFT and the EC are aware of these issues and are currently in discussion about what action, if any, should be taken."
Consumer group Which? has slammed the arrangement, which makes more than 40 million MasterCard and four million American Express cards redundant for the event.
Peter Vicary-Smith, chief executive, Which? says: "We think it's outrageous that some UK sports fans should be discriminated against in this way. We want the London 2012 Committee to take steps to ensure there's a level playing field and that UK consumers have equal access to the Games, whether or not they are Visa cardholders. If it doesn't, we'll call on the government to step in."
In response, Visa says: "There are 91 million Visa cards in the UK of which more than 70% are debit cards. People who don't currently have a Visa debit or credit card are able to obtain a Visa prepaid card, which can be used to purchase Olympic Games tickets and to pay in Olympic Games venues. People can also choose to pay by cash or cheque."