Laws are needed to prevent "mob rule" on the internet and "trial by Twitter", Lord Justice Leveson has said.
He made the comments, his first since publishing his report on UK press standards last week, at a privacy symposium in Sydney, Australia.
Lord Justice Leveson told the meeting new laws would protect privacy and freedom of expression on the internet.
Newspaper editors said on Thursday they would implement his "broad proposals" for self-regulation, without new laws.
The editors said they would report back to the government "very shortly" on how they would "implement the Leveson plan".
They met on Wednesday to try to come up with a plan strong enough to see off demands for a body underpinned by law.
"The editors of all national newspapers met... and unanimously agreed to start putting in place the broad proposals - save the statutory underpinning - for the independent self-regulatory system laid out by Lord Justice Leveson," a statement said.
In his report into press standards and ethics last week, Lord Justice Leveson recommended an independent self-regulatory watchdog for the press, backed by legislation.
Prime Minister David Cameron does not want such a law, but Labour and the Liberal Democrats do.
Lord Justice Leveson was speaking at a University of Technology Communications Law Centre symposium entitled Privacy in the 21st Century.
He said the internet provided a "global megaphone for gossip" and contained an element of "mob rule".
Lord Justice Leveson said the internet was different from mainstream media and that while the BBC apologised for a recent Newsnight programme about child abuse, those "on the internet were not so restrained".
Lord Justice Leveson said that "there was a danger of trial by Twitter" and other forms of social media and it would "take time to civilise the internet".
He added it was likely new laws would be needed to maintain privacy and freedom of expression in the internet age.
His 2,000-page report contained only about a dozen pages dealing with the internet, despite his admission towards the start of eight months of hearings that online material was "the elephant in the room".
The report's suggestion that online material had far less reach and credibility than traditional media was seen as out of touch by some critics.
Lord Justice Leveson told the Sydney conference he would not comment on his report or the reaction to it, which has split the coalition government.
The Australian newspaper quotes him as saying: "This is not because I am concerned about debate," he said, adding that he was "watching developments in the UK with interest".
"I believe the report must speak for itself," he said.