The Federal Trade Commission staff is investigating Boeing Co. and Procter & Gamble Co. for alleged violations of antitrust laws, according to recent commission documents.

The investigation of Boeing, which is being conducted by the FTC's Seattle office, centers on charges that the company placed anticompetitive restraints on its customers and suppliers in the manufacture and sale of aircraft replacement parts.

According to a staff memorandum, the amount of business affected by all the alleged restraints may have totaled hundreds of millions of dollars a year.

The FTC's Bureau of Competition has yet to recommend that complaints be filed against the companies, and the commission could drop the investigations even if the staff recommends further action.

Boeing spokesman Peter Bush acknowledged the investigation yesterday. "We have been cooperating voluntarily with the FTC's Seattle office for more than a year in connection with an informal investigation by that office into the practices of aircraft manufacturers associated with the production and sale of spare parts for commercial aircraft," Bush said.

However, he added, "To the best of our knowledge, the investigation has uncovered no evidence of any anticompetitive practices on Boeing's part, and no allegations have been made by the FTC that we have been involved in such practices."

According to the commission documents, the Seattle staff said it was close to concluding its probe and making its recommendations to the full commission in the very near future.

The probe into Procter & Gamble is being conducted by the FTC's Boston regional office.

Documents indicate the probe focuses on charges that P&G refused to sell its goods on special discounts to stores unless these stores also promised to buy the same merchandise when it was not on discount. Many of P&G's longtime customers complained that they were being hurt by large warehouse stores that purchase their goods solely at discount in order to offer large savings to their customers.

P&G officials were unavailable for comment, and Thomas Campbell, the director of the FTC's Bureau of Competition, refused to confirm or deny the existence of the investigation.

These are just two of the nearly three dozen major investigations now being handled by the FTC's Seattle, Boston, Los Angeles and Denver offices--the four offices which the FTC voted last week to close because of budgetary restraints.

In the Los Angeles office, FTC investigators have spent several years looking into the major motion picture studios to see whether they are using their export trade association to collusively exclude independent American producers from the highly lucrative foreign markets.

Meanwhile, the FTC's Denver staff is looking into charges that a malpractice insurance carrier says it will terminate the insurance of any health-care professional who advertises discounts.

In persuading his fellow commissioners to go along with his proposal to close four of the agency's 10 regional offices, FTC Chairman James C. Miller III has promised that all of the pending cases will be transferred to Washington, where they will be completed.

His aide Campbell agreed. "I have carefully studied every competition case in every regional office we plan to close and have found a place for them in our place in the Bureau of Competition" here in Washington.

Several congressmen, however, are not so sure these cases will be pursued effectively and efficiently once transferred here, so far away from the companies that are being investigated--especially at a time when the agency's travel budget is being cut. Those concerns surfaced in a hearing yesterday by a House Government Operations subcommittee.

"A 40 percent reduction in the commission's regional offices represents a serious and significant retrenchment in the federal government's commitment to protect consumers and prevent anticompetitive practices," charged Rep. Benjamin S. Rosenthal (D-N.Y.), the subcommittee chairman. "I think that is baloney," Miller responded to Rosenthal's charges, thereby sparking an angry reply from Rosenthal.