Lord Justice Leveson has said he is disappointed that the details of private letters he has written are being "openly discussed" in the media.
The judge heading an inquiry into Press standards wrote the letters to give prior notice of possible criticisms in his report.
A spokesman for the inquiry said: "Lord Justice Leveson is disappointed that the contents of confidential letters that he has written are being openly discussed in the Press.
"He wants to make it clear that all recipients of these letters - which are issued in accordance with Rule 13 of the Inquiry Rules 2006 - are obliged by this confidence."
According to The Guardian, the letters were sent to all newspaper groups warning that he expected to rule on everything from privacy to self-regulation.
A source told the newspaper that he had thrown the "kitchen sink" at the Press in the Rule 13 notice, which was around 100 pages long.
The inquiry spokesman added: "These letters are a standard part of inquiry procedures and give private notice of possible criticism in order that recipients can respond before any concluded view is reached.
"By their nature such letters are, of course, one-sided documents and are not intended (as it makes clear) to deal with the positive aspects of the activities of the Press: plainly, no warning is necessary for that purpose.
"The extent to which these letters are being made the subject of comment and, indeed, misrepresentation, is itself not without significance. Meanwhile, the process of providing Rule 13 notices will continue."