Labour MP Tom Watson plans to detail new findings of covert surveillance techniques employed by News Corporation that go "beyond phone hacking".
Mr Watson, MP for West Bromwich East, said the revelations planned at the company's annual shareholder meeting in Los Angeles "will leave the company liable to civil liability but also huge reputational harm".
News Corp officials declined to comment.
Watson has spearheaded a two-and-a-half year probe into phone hacking and alleged police bribery at the company's newspapers. He made the comments to reporters in a conference call from Los Angeles, but gave few details.
He said he will be acting as the proxy for stock owned by the US labour organisation AFL-CIO. He plans to speak at the meeting on Friday and will probably be allowed to do so along with other shareholders.
The meeting represents the first time that 80-year-old chief executive Rupert Murdoch has faced shareholders with small stakes since the hacking scandal broke in early July.
