The head of the Office of Government Ethics said yesterday that a Commerce Department official "went well beyond any permissible course of conduct" last month when he solicited Japanese car manufacturers to hire him to form a trade association to represent their interests against "protectionist and xenophobic" U.S. policies.

Acting ethics chief Donald E. Campbell made the statement as a House Post Office and Civil Service subcommittee began investigating the case of Robert E. Watkins, who served as deputy assistant commerce secretary for automotive affairs and consumer goods until he resigned Oct. 8 after the Associated Press reported the matter.

Commerce Department spokesmen said yesterday that Watkins had left no telephone number and could not be reached for comment.

On Sept. 23, according to testimony, Watkins sent about 500 letters and resumes to companies, including Mazda, Toyota and Nissan, describing himself as "uniquely qualified to establish and lead an automotive association committed to market principles."

Subcommittee Chairman Gerry Sikorski (D-Minn.) said Watkins was invited to testify but refused.

Sikorski said that at the same time Watkins was sending out the solicitations, he was representing the U.S. government as a trade negotiator with Japan and Canada, "negotiations which obviously had a direct, immediate and intimate impact on the foreign companies Mr. Watkins in fact solicited."

Marilyn G. Wagner, the Commerce Department's assistant general counsel and ethics officer, testified that Watkins had spoken to one of her subordinates last June about his plans to seek a job outside the government and was advised that he was required to recuse himself only after a company responded positively to his letter.

But Wagner said Watkins' proposal for setting up the association for foreign firms was never mentioned to her office. "As soon as this letter became public, it gave him the appearance of being in conflict with his role as a policy adviser for trade for the American auto industry."

She called it a "serious mistake in judgment for which he has paid a price in lost wages and reputation. It damaged the image and integrity of the department and raised questions regarding our entire ethics program because the system did not catch or prevent the activity."

Sikorski has asked the Office of Government Ethics to investigate whether Watkins' solicitations violated federal prohibitions against government employes "using their public office for private gain."

"The administration should tell us how much damage was caused to the American negotiating position when one of our negotiators apparently had his eye cocked toward future employment with companies like Toyota, Mazda and Nissan on the other side of the table," he said.