Sports fans who want to use a credit or debit card to buy tickets for the London 2012 Olympic and Paralympic Games will be restricted to using a Visa card, due to an exclusive deal between the Olympic organisers and the credit card payment system.

Payment for the 10 million tickets expected to be sold from 2011 through the Olympic website and other authorised sellers have been restricted to those that run through the Visa payment system.

On the official London 2012 ticket site, it says: "In recognition of Visa's support of the Olympic Games and Paralympic Games, London 2012 is proud to accept only Visa payment cards (debit, credit and prepaid), along with cash and cheques. Sponsor support is crucial to the staging of the Olympic Games and Paralympic Games and the operation of organisations throughout the Olympic Movement.

"London 2012 will also welcome cash and cheques. However, to enjoy the benefit of the quickest and easiest means of payment, see below on how to apply for a Visa card."

Astonishingly the site then goes on to tell customers how to apply for a Visa card, saying "the easiest way to obtain a Visa card is to contact your existing bank which will be able to help you to select and apply for a Visa card that most suits your needs. Alternatively anyone can purchase a Visa prepaid card from a Visa card issuer which can be used immediately. Please visit the Visa website for details."

There are 91 million Visa cardholders in the UK compared to 40 million Mastercard and 4 million Amex cardholders, meaning that some potential buyers will struggle to obtain tickets. The deal also means they will not be able to withdraw cash from ATMs or make purchases at any Olympic sites unless they have cash: the ATMs and payment terminals are also restricted to Visa cards.

Paul Woodmansey, a press officer for London 2012, said the exclusive arrangement with Visa was not "unusual in any way or form. As a sponsor, they gain exclusivity in their sector," he said. "This has been the situation since [the Olympics in] Seoul in 1988."

According to Which?, the restrictions only apply to UK cardholders: non-UK cardholders will still be able to use other cards to buy tickets.

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 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."