John S. Irving, general counsel of the National Labor Relations Board, has joined the ranks of high government officials who may resign because of new ethics legislation that takes effect July 1.

Irving, a 14-year veteran of the NLRB and the Labor Department, indicated that he may leave his government post in a letter to Rep. George E. Danielson (D-Calif.), in which he endorsed a bill Danielson introduced recently to postpone the effective date of the new ethics law.

"I believe that public servants who have acted in complete good faith and at great personal sacrifices are being unfairly and unnecessarily penalized," Irving wrote Danielson. He said that "at the very least... it is unjust to impose on current federal employes post-employment restrictions harsher than existed at the time they agreed to serve the government."

Along with tightening existing ethics rules, the new law bans former government officials from dealings with the government on behalf of a private organization on any matter under the official's former jurisdiction.

Irving said he took the $50,000 general counsel's job in 1975 because of a "desire to serve the public in an agency whose mission I deeply believe in," although existing ethics rules posed some post-employment restrictions, and attorneys, he said, can earn more in private practice.

"My decision might have been different if I had known that my ability to pursue gainful employment in the private sector would be substantially impaired...," he added.

Irving noted a Washington Post report that several other government officials have said they may resign if the new rules take effect as scheduled, and said he, too, "must decide whether or not I will leave the federal service before July 1."

Among the officials who have issued similar warnings are Undersecretary of Health, Education and Welfare Hale Champion and Dr. Donald S. Fredrickson, director of the National Institutes of Health.