The home addresses of all 38,000 runners in Sunday's London Marathon, including those of celebrity chef Gordon Ramsay and leading Labour Party politician Ed Balls were mistakenly published online, organisers admitted Monday.
The details were accidentally released on the marathon's official website and were accessible to anyone logging onto the site on Monday until organisers later rectified the leak.
Ramsay, opposition finance minister Balls and model Nell McAndrew all had their personal details published in the glitch, which was uncovered when a member of the public called a television presenter.
"We apologise for this error, and are grateful to the BBC for bringing it to our attention," Nick Bitel, the chief executive of the London Marathon, said.
"We immediately made sure that the glitch was corrected.
"We do not believe that this has led to a substantial number of individuals' details being accessed by members of the public," he added.
The Information Commissioner's Office, Britain's independent regulatory office dealing with the data protection, confirmed it would look into the leak.
"This is something the Information Commissioner will need to look in to to see how it has come about," a spokesman for the office told the BBC.
"Every case is different and we will certainly be making enquiries."
Explore further: BBC TV programme in row over Nissan electric car