Figures claiming to show the extent of a private investigator's dealings with national newspapers and broadcasters were published on Wednesday.
An analysis of data apparently shows that newspapers made hundreds of requests for information about celebrities, members of the royal family, sports personalities and crime victims, some of which may have been illegal.
The broadcaster said the newspaper asked Whittamore, who was later convicted of illegally accessing personal data, to discover 1,285 ex-directory numbers.
It is claimed the newspaper and the magazine also made other requests - including asking for personal details of the Duchess of Cambridge and her sister Pippa Middleton.
From 2000 - 2003 it is reported that the Daily Mirror requested 984 pieces of information, including 660 ex-directory number searches and 19 criminal record checks.
It added that much of the information bought was legitimate but other requests may not have been - such as requests for ex-directory numbers, numbers of family and friends, police record checks and vehicle checks. These searches could be deemed illegal unless it could be shown they were in the public interest.
ITV News also claimed invoices showed the investigator charged News International £490,739 between 1995 and 2003.
Trinity Mirror commissioned him for £376,918 of work, while Associated Newspapers spent £268,311.
Other newspaper groups also paid him tens of thousands of pounds to conduct investigations for them.
Whittamore's Hampshire home was raided by investigators from the Information Commissioner's Office (ICO) in March 2003. He was convicted of illegally accessing data and received a conditional discharge at London's Blackfriars Crown Court in April 2005.
An ICO spokesman it had provided the Leveson Inquiry into press standards with "extensive evidence" relating to Motorman, adding: "We now await the Inquiry's outcome, and will respond appropriately to any relevant recommendations.
"While we had reason to believe that some of the material could only have been obtained via unlawful means, the press are able to claim a public interest defence. This could explain an apparent discrepancy in figures."
A spokesman for Associated Newspapers said the Information Commissioner's 2006 report, What Price Privacy Now, recognised that many cases would have been covered by public interest defences.
He said: "Indeed it is a requirement of both the law and the PCC Code that matters concerning individuals in the news should be put to them before publication to ensure accuracy and give the opportunity to offer comment.
"To do this it is vital to trace addresses and telephone numbers which in the main could be obtained through legal means."
He added: "The Information Commissioner urged all industries and their regulators to review practices to ensure compliance with the Data Protection Act.
Following this, Associated Newspapers banned the use of inquiry agents five years ago.
"It is a condition of employment that our journalists comply with the PCC code of practice and the Data Protection Act. Any breach of either the Code or the Act is a sackable offence."
A Trinity Mirror spokesman told ITV News: "The detail to which your programme refers was subject of a police investigation in 2003 when no action was taken against any journalist."
He added that it is company policy to comply with the law and the Press Complaints Commission code.
A News International spokeswoman told the programme: "The information you refer to you was the subject of a report by the Information Commissioner's Office in 2006 and has been examined extensively by the Leveson Inquiry in recent months. News International has given detailed evidence on these matters.
"There is a public interest defence available for any potential breach of the Data Protection Act and you do not have the information necessary to make any judgment on specific cases."
Prime Minister David Cameron set up the Leveson Inquiry last July in response to the disclosure that the News of the World hacked murdered schoolgirl Milly Dowler's phone after she disappeared in 2002.