A senior federal housing official resigned yesterday following an investigation into his receipt of at least $80,000 in fees from a group that sells books and tapes on how to make money in real estate.

Gordon D. Walker, deputy undersecretary of the Housing and Urban Development Department, announced his resignation a day after the Justice Department declined to pursue criminal charges in the case. HUD Secretary Samuel R. Pierce Jr. still must decide whether to seek financial restitution from Walker based on a report by the agency's inspector general.

The Washington Post reported last month that Walker, who joined HUD in 1981, gave numerous lectures for the National Institute of Financial Planning while on official HUD trips that were paid for by the government.

From 1982 to 1984, the institute paid Walker $80,000 to $200,000 in "royalties," according to his financial disclosure statements.

Walker, who is returning to his Salt Lake City development business, has produced four audio tapes and a book for the firm, which sells them for up to $59.95 apiece along with other cassettes featuring "the biggest names in real estate investing." Walker's book is called "Develop Your Way to Success."

"I stayed longer than I originally intended because of criticism and questions raised concerning my preapproved personal activities," Walker said in a letter to Pierce. "However, now that the Justice Department has cleared me of any wrongdoing in connection with these activities, I can leave feeling that the questions are resolved."

Walker's appearances at seminars promoting the institute's books and tapes were approved by a HUD lawyer. But sources said HUD officials had been surprised to learn that he earned about $75,000 in 1984 for more than 30 speeches around the country, and that he had been widely expected to resign when the probe was over.

Walker, who earns $72,300 overseeing HUD's 81 local offices, declined to respond to questions. But his attorney, Joseph B. Tompkins Jr., said there was "no substance" to allegations that Walker received double payments from both HUD and the Salt Lake City-based institute for six to eight trips.

Tompkins said the group paid Walker nearly $4,000 in travel expenses on those HUD trips, but later deducted the amounts from Walker's royalties to avoid double billing.

Tompkins said Walker "did in fact meet with HUD people or conduct HUD business" on each trip and spoke at the seminars on his own time.

He said it was "largely a coincidence" that the group's seminars overlapped with Walker's travel schedule, adding that there is no need for Walker to reimburse the government for the trips.

A typical package promoted by the institute is called "Six National Real Estate Experts Show YOU How to Create Wealth." HUD officials have criticized some of the material as misleading.