A senior database administrator in the US has admitted stealing the details of 8.5 million customers over a period of five years.

William G Sullivan worked for Certegy Check Services, which offers financial authorisation services to retailers. He was entrusted with defining and enforcing data access rights.

"Some of the stolen records contained only identifying information such as name, address, telephone number and, in some circumstances, date of birth," said a statement from Certegy.

"However, many records contained personal financial information, and we are in the process of notifying those consumers whose financial information was included in the stolen data."

According to information presented to the courts, Sullivan is alleged to have sold the information to data brokers for a total of $580,000 (£284,600).

The 54 year-old entered a guilty plea in a Federal court in Tampa, Florida. As part of his plea bargain, Sullivan has promised to help with the continuing US Secret Service investigation into the case, and to pay damages to the victims.

Sullivan's agreement with the authorities will see him imprisoned for less than the maximum five years, although his jail sentence has yet to be set.