The information commissioner Christopher Graham has said he is "very disappointed and really very angry" that part of the data from the Operation Motorman files has been leaked online, adding that the move is "deeply irresponsible".
Speaking on BBC Radio 4's World at One programme, Graham was asked to respond to the news that some of the data - with redactions - from the 2003 information commissioner's inquiry into newspapers' use of private investigators, had been published on the Guido Fawkes blog.
Earlier today the Information Commissioner's Office (ICO) issued a statement accusing the movement of the files "into the public domain" as causing "a serious violation of many people's privacy".
"The issue of publication is being considered by the Leveson Inquiry and it's most unfortunate that Guido Fawkes has chosen to jump the gun. The ICO will now consider what further steps it should take in the face of this apparent breach of the DPA."
Speaking on the World at One Graham added that the related issues are a "very grey area and just putting stuff on the internet doesn't help".
Graham also told the World at One that under the Data Protection Act those who believe their information may be in the files can apply for a "Subject Access Request", and that therefore alleged "victims" have been "taken care of".
"We are waiting to hear from Leveson whether he thinks this information should be published more generally in redacted form or whatever.
"... We have to look at each case individually, you can't just stick it up on the web and say 'well what do you think of that then?'".
In March the Hacked Off campaign called on Lord Justice Leveson to publish the data from Operation Motorman, once personal details have been redacted.
Today Hacked Off said in a statement that it was not involved in the publication of the files and is not in possession of them.
Founder of the campaign Martin Moore also spoke to the World at One, adding that the campaign had warned that if the files were not "opened up and redacted" then they may "come out unofficially".
The campaign added in its earlier statement: "Our view is that the full files should be professionally redacted and published in as clear a manner as possible by either the Information Commissioner’s Office (ICO) or the Leveson Inquiry, and the ICO should proactively contact the victims.
"It is important to note that the complete files are already in the hands of the inquiry and all of the national newspaper groups, and that many other people have had access to parts of the files. This material is a secret only from the public and in our view partial disclosures of this kind, and of the kind published by ITN days earlier, were inevitable given the official refusal to redact and disclose.
"To avoid the emergence of a partial and possibly misleading or unfair picture of press data-mining, that official position should be reversed promptly and a commitment should be given to publish as soon as possible a complete version of the Motorman records, with only those redactions that are necessary to protect the privacy of those who were intruded upon."
At the time of publishing the files the Guido Fawkes blog said: "Guido is not commenting further for the moment" but has counter-criticised the ICO via Twitter.