Some 500 participants in a National Conference on Organized Crime were urged last week to aid in the development of a national strategy to combat the problem, but by the time the meeting concluded Friday, it seemed evident that a political battle was heating up over who should lead the assault on the underworld.

The day-and-a-half-long conclave, sponsored by the University of Southern California, brought together law enforcement officials, academicians and journalists from around the country.

Delivering the keynote address by telephone hookup from Washington, Sen. Sam Nunn (D-Ga.), chairman of the permanent subcommittee on investigations, pledged that his subcommittee, which a staff of investigators and former prosecutors, would "put the spotlight on organized crime in this country," beginning in January.

Martin L. Steinberg, the subcommittee's chief counsel, announced that the panel would soon issue a report on misuse of Teamster pension funds and arson-for-profit schemes. He also announced plans for investigations into stolen cars rings and the use of profits made from the sale of narcotics.

Also addressing the conference was Sen. Dennis DeConcini (D-Ariz.), who has introduced a resolution, pending before the Senate rules Committee, that a select committee be established to investigate narcotics and organized crime.

DeConcini said he has begun a series of hearing into the subject under the auspices of the Senate Appropriations Committee.

Charging that "the permanent subcommittee has not done the job," and that Nunn's work on the Armed Forces Committee would prevent him from giving his full attention to mob activities, DeConcini said he would ask the president to appoint a "czar" to direct the battle against organized crime and narcotics traffickling, should his select committee resolution fail.

Arguing that Americans and their government have all but ignored mob syndicates since the 1960s, DeConcini said, "As a business, the Mafia yields conservatively 10 times the profits of Exxon, the nation's largest corporation.

"Organized crime is becoming the No. 1 investor American business," he said. "Once it infiltrates deeply into the legitimate business community, it is no longer controllable."

Asked about DeConcini's resolution, Nunn replied that it was his "obligation to point out we're already involved in that area."

At a summary news conference attorney Michael J. Aguirre, the convention organizer, obviously miffed that Nunn had not attended the meeting, called for "total support for DeConcini."