The House Subcommittee on Communications will expand its probe of the three major television networks' relationship with professional and amateur athletics. Rep. Lionel Van Deerlin (D-Calif.) announced yesterday.

The investigation, which arose as a result of the CBS "winner-take-all" tennis series: the United States Boxing Championships televised by ABC, and NBC's contract with the Soviet Union for the 1980 Olympics, will now also examine network contracts with the National Football League, National Basketball Association, National Hockey League, professional baseball and the National Collegiate Athletic Association.

"We will put particular emphasis on contracts for exclusive telecasts," Subcommittee chairman Van Deerlin said. "We are also concerned with exclusive contracts between the networks and athletes." He cited boxer Sugar Ray Leonard's contract with ABC and football quarterback Fran Tarkenton's pact with NBC as examples.

"We're worried about the effect exclusive contracts like these might have on the network's coverage of the athlete and what effect it would have on the other networks' coverage of him," Van Deerlin said. "There's something unwholesome about networks getting into ownership of athlete's contracts. People expect an independent picture of events from the networks and we want to make sure they're getting it."

As a result of the expanded investigation, the Subcommittee has hired Phillip R. Hochberg, 36, an attorney with O'Connor and Hannan. He will take a four-month leave of absence from the firm to serve as special counsel to the Subcommittee.

Hochberg has represented the NHL and NBA. Van Deerlin said there would be no conflict of interest, however: "Mr. Hochberg will cease work for those clients during his tenure here. In addition, any portion of the investigation relating to the NHL, NBA or any of Mr. Hochberg's former clients will be handled by someone else on the staff."

Van Deerlin said that if the panel decides legislation is needed to remedy any problems uncovered by the investigation, it would probably be included in the subcommittee's revision of the 1934 Communications Act. Revising that act is the main project of the panel.

Lou Frey (R-Fla.) the ranking minority member on the subcommittee, said that he hoped some form of an antiblackout law - the original one having expired at the end of 1975 - would be included in these revisions and that they would be made during the current session.

Hearings are expected to start within the next month.