JACKSONVILLE, Fla. —Phil Mickelson filed a lawsuit against an Internet service provider in Canada to learn the identity of a person who has been posting “vexatious statements” the four-time major champion says is a deliberate attack on his reputation.

“I’m all for freedom of speech, but I won’t tolerate defamation,” Mickelson said yesterday after shooting a 68 in the first round of the Phoenix Open.

In his lawsuit against Videotron S.E.N.C, Mickelson cited comments posted on Yahoo! Sports from Nov. 11 to Nov. 12, in which one or more persons under the pseudonyms “Fogroller” and “Longtitude” made statements that allege, among other things, Mickelson’s wife had an affair and that he fathered an illegitimate child.

Mickelson said he is a victim of defamation. He is asking the court to force Videotron to identify the person.