Thousands of ticketholders have already struck lucky, upgrading to tickets for major events including swimming and athletics finals, and in around 200 cases the hottest ticket of all, the men’s 100m final.
Locog said the decision to award 100m final tickets was taken because one of the synchronised swimming sessions was on the same afternoon as the event, August 5.
In an attempt to minimise disruption to travel plans that might already be in place, Locog decided to award athletics tickets on a first-come first-served basis.
Because Locog will bear any discrepancy in the ticket prices, it raises the possibility that some ticket holders could see the most eagerly awaited event of the Games at a discount of at least £55.
The cheapest ticket for the synchronised swimming was £20 compared to £75 for the main stadium.
The revelation of the error comes two days before Locog unveils its ticket resale system, an online exchange designed to allow fans to swap unwanted tickets rather than sell them to touts.
In a statement Locog said: “As a result of finalising the seating configurations in our venues and reconciling the millions of Olympic and Paralympic ticket orders against the seating plans for around 1,000 sporting sessions, we have discovered an error in seats available in four Synchronised Swimming sessions.
“In December we contacted around 3,000 customers who had applied for tickets in the four sessions during the second-round sales process. We are exchanging their synchronised swimming tickets for tickets in other sports that they originally applied for.”
While the mistake had left some ticketholders welcoming an early Olympic Christmas present, it came as a significant embarrassment to the organisers.
The ticket allocation process has proved the most controversial aspect of London 2012 planning, with criticism of the failure to get tickets to more members of the public.
The level of information about how many tickets were available was also criticised, with organisers yet to confirm how many members of the public will be in the main stadium, aquatic centre and velodrome for the major finals.
The system was also felt to favour those able to risk large sums of money on a big number of high-value tickets in the ballot in the hope of receiving a small number of tickets.
Locog has defended the process used to allocate tickets and has received a significant endorsement in the massive demand for tickets for all sports.
It has already banked £537 million of the £670 million target for ticket revenue, and around 1.2?million tickets, mainly for football, are due to go on sale in April.
About 6.6 million tickets will be available to the public across the 26 Olympic sports, with the remaining 2.2?million going to sponsors, the International Olympic Committee, officials and competing nations.