London 2012 organisers have been criticised by consumer group Which? over their deal with card firm Visa which prevents British sports fans using other cards to buy tickets.

Which? says it is "outrageous" that British Olympic fans will not be able to pay for tickets by MasterCard or American Express or withdraw cash at any Olympic sites unless they have a card which runs on the Visa payment system.

London 2012 say they are looking at other payment methods for tickets, and defended the Visa deal saying they would not be able to raise the funds to stage the Games unless they offered such exclusive agreements to corporate sponsors.

Peter Vicary-Smith, chief executive of Which?, said: "We think it's outrageous that some UK sports fans should be discriminated against in this way.

"We want the London 2012 organising 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."

Organisers added that cash machines accepting all cards will also be provided at access points to Olympic venues.

Visa said fans could obtain a 'pre-paid' card with credit to buy tickets or use other payment methods.

A Visa statement said: "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.

"Visa is an integral part of the Olympic Games and has been a committed partner for almost 25 years. At every Olympic Games, Visa creates and manages the entire payment system infrastructure and network throughout all Olympic Games venues."