Vivendi Universal says fears of Internet vote rigging at its annual meeting last week could throw suspicion on the Paris stock market and shareholders' meetings that use electronic voting.
The company is taking legal action after discovering "systematic dysfunction" in the electronic voting system. It is filing a claim with the Paris courts against unspecified hackers.
During the meeting, chief executive Mr Jean Marie Messier survived as head of the world's second-largest media group, but a 1.2 billion stock options plan was voted down.
The electronic voting system used at the meeting allowed investors three options - to vote yes, no or to abstain.
Vivendi said its suspicions were aroused by an abnormal level of abstentions, which accounted for 20 per cent of the votes cast.
The company said: "This incident is extremely serious in that it could throw suspicion on the entire Paris stock market and all the shareholders' meetings currently using electronic voting, and possibly moving to Internet voting in the future.
The allegations of vote tampering came as Vivendi revealed an £8.4 billion loss, the biggest in French corporate history.