Nearly 100 companies and individuals who used rogue private investigators are to be probed by the data watchdog.
A list of 98 clients compiled by the Serious Organised Crime Agency (Soca) as part of its inquiry into private eyes has been handed to the Information Commissioner's Office (ICO). A further nine clients have been withheld by Soca at the request of the Metropolitan Police.
The so-called " 'blue-chip hacking'' list, drawn up during Soca's Operation Millipede, which led to the conviction of four private detectives for fraud last year, was recently subject to a row over transparency after it was handed to MPs on condition the names were not published.
More than 20 files of material have been passed from Soca to the ICO, including correspondence between clients and the private investigators and receipts for payments.
The data watchdog is to write to all individuals and organisations listed to find out what information the private investigators provided and whether the clients were aware the law might have been broken.
A criminal prosecution for unlawfully obtaining or accessing personal data is a possibility, although c ivil action for breaching the Data Protection Act, punishable with a fine of up to £500,000, is considered to be more likely.
The ICO said the initial phase of the investigation will take several months.
A list of 102 firms and individuals linked to rogue private investigators was handed from Soca to the Home Affairs Select Committee on condition names were not revealed.
A total of 22 law firms feature on the list, alongside several insurance companies, financial services groups and two celebrities, among others.
Up to 100 individuals may have had their details accessed by the private investigators, Soca's director general Trevor Pearce previously revealed.
Of the 100 potential victims, 91 have been contacted by Soca, Mr Pearce said.
Mr Pearce and Soca's interim chair Stephen Rimmer are to appear before the Home Affairs Select Committee tomorrow.
Chair of the Home Affairs Select Committee Keith Vaz MP said " The Committee had asked for the Commissioner to be involved from the time of Soca's appearance in July.
"We need an explanation as to why it has taken Soca so long to pass the information to the ICO. It is deeply concerning that these files were only passed to him 24 hours before Mr Pearce's appearance before the Committee.
"It is particularly puzzling given that Mr Pearce told the Committee that he would be passing on the files to the ICO once Operation Tuleta, scheduled to continue until at least April 2015, was finalised.
"The Commissioner has in the past said that the ICO simply does not have the resources to investigate all the cases they receive and I will be writing to the Ministry of Justice asking them to ensure that such an important investigation has adequate funding."