A total of 19 clients of rogue private eyes will be investigated for illegal activity, the data watchdog has confirmed.
In a letter to Keith Vaz MP, Information Commissioner Christopher Graham said 125 victims were believed to be affected by the companies and individuals under criminal investigation for data protection breaches.
A list of clients of rogue private detectives will not be published by MPs "for the time being" after the data watchdog intervened.
Information Commissioner Christopher Graham urged the Home Affairs Select Committee not to publish a list of 102 organisations and individuals who used rogue investigators while his office conducted its own investigation.
Committee chairman Keith Vaz MP said: "The Information Commissioner has given the committee an explicit commitment that he will pursue this matter to its appropriate end and that the victims will receive justice."
Vaz said Graham would appear before the Committee after his "scoping exercise" so that MPs could assess whether the investigation "fulfils all that is required".
The Information Commissioner has been called to give evidence to MPs over the publication of a controversial list of clients of rogue private investigators. Christopher Graham will appear before the Home Affairs Select Committee tomorrow.
"Following representations that the Committee has received from the Information Commissioner we have called him to give evidence to the Committee on Tuesday.
"We will hear his views on the issue of the publication of the Soca list and related matters."
SOCA provided Mr Vaz's committee with the list - containing 102 firms and individuals, including blue chip companies, law firms and financial services groups - on condition that the names are not revealed, sparking a row over transparency.
The Information Commissioner has written to the chairman of the Home Affairs Select Committee urging "patience" after he threatened to publish the names of clients of rogue detectives, compiled by the Serious Organised Crime Agency.
Writing in a blog Mr Graham said he has written to Keith Vaz urging him not to go through with his threat to publish the names of the clients on the list by midday today.
"It's not clever to start a criminal investigation by publishing the names of everyone and everything you're investigating.
"That's why we've stated we're not publishing the list at this stage, and why I've written to Keith Vaz MP to urge similar patience on the part of his Select Committee.''