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.
MPs had threatened to release a full list of 102 of those involved if action was not taken.
A list of clients of rogue private detectives will not be published by MPs "for the time being" after the data watchdog intervened.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 Home Affairs Select Committee will publish a list of 102 clients of rogue private investigators on Monday if the Serious Organised Crime Agency (Soca) does not do so first, chairman Keith Vaz has said.
Keith Vaz, chair of the Home Affairs Select Committee, has said the actions of Cabinet Secretary Sir Jeremy Heywood over material held by The Guardian was "unprecedented" and called for a full statement from David Cameron to explain the government's involvement in the incident:
Home Affairs Select Committee chairman Keith Vaz has written to the Met Police's Assistant Commissioner Cressida Dick to ask if the force has any further interest in the companies on a list of names linked to rogue private investigators.
He has asked Ms Dick, as well as the Information Commissioner's Office, to confirm when the public will be able to see those names, whose identities are currently being protect at the behest of the Serious Organised Crime Agency (Soca.)
The list, which was created by Soca, was passed to the Home Affairs Select Committee on strict confidentiality grounds - prompting Mr Vaz to demand an explanation as to why it should be kept secret.
It breaks down firms that featured in evidence in prosecutions of Operation Millipede, the Soca investigation that led to the conviction of private detectives for fraud, as well as firms that were relevant to the inquiry but not used in evidence.
Chairman Keith Vaz said the Home Affairs Select Committee "remains concerned" after it was handed a list of 102 names of companies and individuals linked to rogue private investigators.
The Committee remains concerned that it holds a list that Soca [Serious Organised Crime Agency] has classified as secret, even though it is evidence given as part of our inquiry.
This is an important step forward in establishing the facts.
Mr Vaz also confirmed there are five organisations or individuals on the list who are being investigated as part of Operation Tuleta, Scotland Yard's investigation into allegations of computer hacking.
Home Affairs committee chairman Keith Vaz said it is "worrying" that Police and Crime Commissioners "seem able to side-step the statutory process for dismissing a chief constable".
Mr Vaz said: "Police and Crime Panels should make more active use of their powers to scrutinise decisions such as this.
"We will be returning to this area when we carry out our next major inquiry into Polic eand Crime Commissioners, towards the end of this year."
A report by an influential group of MPs has revealed that the number of unresolved immigration cases has grown to more than 500,000.Read the full story ›
The backlog of immigration cases at Britain's border service has hit half a million people and at the current rate of progress will take nearly four decades to clear, a group of MPs has warned.
Home Affairs Select Committee chairman Keith Vaz said: "At the current rate it will take 37 years to clear and the Home Office cannot confirm that this is the last of the backlogs."