The chairman of the public inquiry into press standards has warned editors against targeting people who speak out against intrusion by journalists.
Lord Justice Leveson said his team would monitor newspaper coverage over the coming months for any evidence that witnesses to his hearings were being singled out for negative stories.
Speaking at the opening of his inquiry, the chairman stressed that the freedom of the press was "fundamental" to the UK's democracy and way of life.
He also recognised that there was a "great deal to applaud" in Britain's present press, adding: "I certainly do not intend to limit my consideration to activities which could be the subject of criticism."
But he stressed that he would be alert to any evidence of newspapers victimising witnesses who complained about press intrusion.
Lord Justice Leveson said: "Concern has specifically been expressed that those who speak out might be targeted adversely by the press as a result. I have absolutely no wish to stifle freedom of speech and expression, but I anticipate that monitoring will take place of press coverage over the months to come.
"And if it appears that those concerns are made out, without objective justification, it might be appropriate to draw the conclusion that these vital rights are being abused, which itself would provide evidence of culture, practice and ethics which could be relevant to my ultimate recommendations."
Prime Minister David Cameron set up the Leveson Inquiry in July after revelations that a private detective working for the News of the World hacked the phone of murdered schoolgirl Milly Dowler.
Lord Justice Leveson, a Court of Appeal judge, said the task of his investigation could be summed up in one simple question: "Who guards the guardians?"
The first part of the inquiry is looking at the culture, practices and ethics of the press in general. The second part, examining the extent of unlawful activities by journalists, will not begin until detectives have completed their work and any prosecutions have concluded.