One day after Marvelous Marvin Hagler successfully defended his middleweight title against Mustafa Hamsho, knocking out the No. 1 challenger in the third round of a scheduled 15-round bout, the World Boxing Council voted unanimously to strip Hagler of his title for disregarding its rule limiting championship fights to 12 rounds.

Until the decision, which came on the closing day of the WBC's convention in Montreal, Hagler had been an undisputed champion, recognized by the WBC, the World Boxing Association and the International Boxing Federation. The Hagler-Hamsho fight was sanctioned by both the WBA and IBF.

Jose Sulaiman, the WBC president, said he had repeatedly asked Hagler to conform to the 12-round rule but had received no response.

At a press conference Thursday, and in private interviews afterward, Hagler said he thought "world title fights should all be scheduled for 15 rounds" and that "no matter what they (the WBC) decide to do, everybody knows who the champion is. All this does is confuse the boxing public, and it's time every division had only one champion.

"Look at the heavyweightdivision," he continued. "There's such a split with all the different champions, people start to lose interest and can't figure out who's what. But they know me as the undisputed champion. I am the champion, and will continue to be, no matter what they decide."

The WBC adopted the 12-round limit for championship fights on Jan. 1, 1982, after South Korean lightweight Duk Koo Kim died following a WBA-sanctioned title fight with Ray Mancini.

Sulaiman told The Associated Press, "We are going to be attacked by a sector of the world, we are going to be rapped and criticized . . . But I believe that above these attacks must rest the honor and respect that we have to our principles of integrity, justice and fairness."

Promoter Bob Arum said today he hopes to pit Hagler against Thomas Hearns in Las Vegas in March, with each fighter earning $5 million. Against Hamsho, Hagler made $1.45 million.

Hagler was unavailable for comment today, but Goody Petronelli, his comanager, told AP that Hagler already had litigation pending against the WBC concerning the 12-round rule and the council's past threats to strip him of the title. There will be a hearing on the matter Thursday in U.S. District court in Brooklyn.

The technical knockout against Hamsho came at 2:31 of the third round. Hamsho's manager, Al Certo, who had watched disconcertedly as his fighter hit the canvas earlier in the round, only to rise and be battered again by Hagler, decided Hamsho could take no more and climbed through the ropes, automatically ending the fight. Certo covered his fighter as referee Arthur Mercante called an end to the ugly affair.

"I put punches together and meant to break his head," Hagler said afterward. "I don't want to ever see that man's face again."

Hamsho fought Hagler three years ago and endured 11 rounds with the 160-pound champion, who so brutalized Hamsho that night that the challenger needed 55 stitches to close his wounds. Back then, Hamsho promised trainer Paddy Flood there would be a next time and that he would avenge the loss. Flood called Hagler "a bum," and said, "That bum didn't beat you. You beat yourself."

It has been more than a year now since Flood died of a brain hemorrhage, but Hamsho claimed his friend's spirit continued to dwell in him. During a fight against Wilfred Benitez, which Hamsho won on a one-sided decision, Hamsho claimed to actually hear his trainer urging him on, instructing him how to approach his game opponent.

But Hagler, a vicious competitor who relies on intimidation to suppress the will of his opponents as much as he does speed and strength, considered Hamsho's talk of ghosts "ridiculous." Only two men and a referee occuppy the ring, and, as he said after the fight, you "can't leave a fight up to the referee and the judges. The only way to do it is my way."

Early in the fight, Hamsho had used a head butt to rattle the champion, and a couple of forearms drew a warning from Mercante. Enraged, Hagler stalked Hamsho around the ring. When Hagler opened up with his punching in the third round, it was only a matter of time before Hamsho collapsed under the barrage.

Earlier in the week, Hagler's camp had objected to three women judges working the fight. The New York State Boxing Commission settled on only Eva Shain and placed the other two women officials in a preliminary bout in which Mike McCallum won a unanimous decision over Sean Mannion for the WBA junior middleweight title.