Jack Valenti, president of the Motion Picture Association of America, and MPAA attorney Louis Nizer last week paid visits to the Justice Department Anti-Trust Division and the Federal Trade Commission to file complaints about Time, Inc.'s Home Box Office's alleged "monopolistic position" in the pay-cable television field.

Valenti and Nizer spent about 40 minutes with Justice Anti-Trust Division head John H. Shenefield and three of his aides Wednesday.

After that, they went to the FTC to speak with Competition Bureau Director Alfred F. Dougherty and some of his aides.

According to an informed source in the Justice Department, Nizer promised to supply the government shortly with "a paper that outlines the whole situation."

"We'd glad to look at the paper," the source said, "but I have to admit that he didn't tell us anything new at the meeting."

The source said that the meeting was not considered important enough to "have a major audience with most of the staff present."

"We are considering what they told us and reviewing it," said Justice Department spokesman Mark Sheehan. "Although I would not call it an investigation, there are some civil investigations being conducted, but I don't want to imply that HBO is being investigated."

Valenti and Nizer claim that HBO is dominating the pay-television-supplier market. Firms in that market supply various cable systems with films and special events on a contract basis.

Of an estimated 12.5 million cable television customers, 1.1 million receive such services from HBO or other suppliers.

In a telephone interview last night, Valente confired the meetings, but would not discuss the details. He said that in this case he is not representing two MPAA members, Warner Bros. and Columbia Pictures, at their request.

Warner Bros. owns cable operations.

Reached at his New York office yesterday, Nizer confirmed the meetings "to lodge our complaint with respect to the monopolistic position of HBO."

Nizer said that ever since HBO bought out a competitor, Telemation Program Service, more than a year age, the Time, Inc. subsidiary has had "over 80 per cent of the market. Prior to that they had 60 per cent."

Valenti is representing the members of the MPAA, the movie makers. Many first-run movies are shown on pay cable television.

Five years old, Home Box Office is expected to have its first profitable year in 1977. It distributes its programming to 341 affiliated cable systems, although it does not own any cable systems itself.