The personal details of thousands of runners, possibly including politicians and celebrities, were made available to the public yesterday after a security breach on the London Marathon website.
Organisers were made aware of the breach yesterday afternoon after it emerged that they had published the home and email addresses of some of its 38,000 entrants online.
The matter was revealed by the BBC after a television presenter was apparently contacted by a member of the public who found her details online. High-profile entrants to Sunday's event included shadow Chancellor Ed Balls, the singer Will Young and the chef Gordon Ramsey.
The error was rectified yesterday afternoon but it was not known for how long the data was available. Last night, organisers tried to play down the incident which appeared to be a breach of the Data Protection Act and can amount to a civil or criminal offence.
A spokesman told the BBC: "This is something the Information Commissioner will need to look into. It's the reasons why these things come about that determine the course of the investigation. Every case is different and we'll be making enquiries."
Nick Bitel, chief executive of the London Marathon, apologised for the breach, adding: "We don't believe this has led to a substantial number of individuals' details being accessed."