Watson, the Labor Party member who helped bring the phone-hacking to light, said he believes the illegal activities were limited to News International newspapers and weren't representative of the industry at large, The Daily Telegraph reported Friday.
Watson's pursuit of News International, the British unit of Rupert Murdoch's News Corp. media empire, for more than two years led to the revelation that the cellphone of slain schoolgirl Milly Dowler was hacked.
He said he will try to "force the truth" from News International and predicted the scandal could expand into e-mail hacking, the Telegraph said
"[It] wouldn't surprise me one bit if it is discovered that there are people who know about how to plant Trojans [malicious programs] on hard drives on computers to obtain e-mail information, which in many senses is a far more serious crime," Watson said.
Watson said he thinks the scandal could be alive for "at least three more years."
He said the public likely would be shocked by more disclosures of phone-hacking.
"I think there are many more clearly criminal invasions of privacy that will come out," he told the Telegraph.
Speaking for the first time since he questioned Murdoch and his son James Murdoch during committee hearings this week, Watson said he "felt sorry for Rupert Murdoch," who the lawmaker said was "beginning to lose grip of his media empire."
"He's an immensely gifted individual -- very innovative," Watson said. "But the utter ruthlessness with which his companies prosecute their case, he's got to answer for that."