The company said the breach did not happen due to a hack but occurred because its database was incorrectly configured, allowing unauthorised access.
The information in the database did not include passwords or financial details but did contain names, email addresses, phone numbers and details of customers’ contracts with the service.
However, the independent company that alerted Virgin to the breach found details that linked some customers to ‘explicit websites’, it told MailOnline.
Virgin Media is blaming the error on the negligence of a staff member who did not follow correct procedures.
The information was accessible from April 2019 until February 28, 2020.