Richard Desmond has told MPs that the Mail on Sunday, Mirror and the People were likely to have practised phone hacking as he gave evidence to a parliamentary committee.
The chairman of Express Newspapers and owner of Channel 5 told the Joint Committee on Privacy and Injunctions on Monday he had "heard internally" about newspapers other than the News of the World.
"I know that the News of the World were hacking because the guy had been in prison… And we always heard internally, I don't want to sound like Hugh Grant, we'd always heard about the Mail on Sunday and heard internally about the Mirror. We'd always heard internally about the People."
The controversial media magnate also said that he believed the PCC should be reformed into a "voluntary" structure, telling the joint committee: "Surely the world must be better by having a free press.. but from time to time there will be problems.
"Let's have a professional body that we can all take advice from and work within a framework, without being told 'oh no, you can't write about Conrad Black' or, 'you can't write about MPs' expenses' because of this, that and the other."
He told MPs and peers he supported editors being taken off the regulatory body partly because "[Paul] Dacre wouldn't like it".
Express newspapers left the PCC in January 2011 - a decision Desmond claimed he was "very pleased" with.
Desmond, who recently said Daily Mail editor Paul Dacre could "go f**k himself" , said he would consider Dacre "immoral" and accused his paper of hypocrisy.
He said Dacre was "absolutely wrong" to suggest tabloid newspapers were dependent on stories about people's private lives.
"For him to think that invading people's privacy and ruining people's lives is a good thing to do."
The Fleet Street heavyweight added: "He's living in the past... He's just, he's fooling himself."