Visa has a controversial exclusive deal with the London 2012 Olympics and Paralympic organisers that prevents fans using other cards to buy tickets.

But yesterday many found that even having a Visa card did not guarantee them a ticket. Visitors to the official ticket Web site could not complete orders if their Visa cards are set to expire before the end of August.

The problem has occurred because, although people can now begin ordering tickets, they will not pay for them until later in the year.

In a statement, Visa Europe says: "We would like to apologise for any inconvenience caused to those cardholders who are having problems applying for London 2012 tickets."

The firm adds: "While we are aware that cards which expire before August 2011 are not currently being accepted, as a priority we are working closely with all relevant parties to resolve this issue as soon as possible."

Until a fix is found, those affected are being told they can use other methods, including a Visa pre-paid card or a paper obtained from Lloyds TSB branches.

Visa isn't the only official Olympic partner to be embarrassed this week. Another glitch saw the 2012 countdown clock in Trafalgar Square, sponsored by official timekeeper Omega, stop only a day after it was unveiled.

Update In a statement released late Wednesday, Visa says: "From Monday 21st March, all Visa cards with an expiry date of May 2011 or later will be accepted by the London 2012 ticket application website. Any Visa cardholders with an April expiry date will receive a replacement card before the ticket registration deadline of 26th April. This means that all Visa cardholders will be able to apply for tickets before the 26th April deadline.

"For those affected cardholders who do not wish to wait until Monday, there are a number of alternatives including using a Visa prepaid card."