HE SENATE Labor Committee was under standably miffed two weeks ago when the FBI sheepishly reported that it had unearthed some file information relating to possibly illegal activities involving Secretary of Labor Ray Donovan's former firm. The committee's temper is unlikely to have been sweetened by the Justice Department's more recent refusal to provide it with tape extracts relating to dealings between that firm and an alleged mobster.

The FBI had assured the committee after Mr. Donovan's prolonged confirmation hearings last year that everything it knew that was relevant to the matter had been aired during the hearings. That turns out not to have been true. As a result, the Senate was deprived of its opportunity to review the full range of evidence relevant to Mr. Donovan's fitness for office--a matter much broader than the question of criminal activity.

Whether or not the additional information might have changed the committee's mind about confirming Mr. Donovan, the action for the moment has moved to another jurisdiction. Last December, as you may recall, a special prosecutor was appointed under the Ethics in Government Act to look into allegations of illegal union payoffs involving Mr. Donovan that had surfaced from other sources.

The Justice Department sought at that time to limit the investigation to a single allegation of a $2,000 payoff. But the panel of federal judges that appointed Leon Silverman as special prosecutor extended his authority to include any other alleged violations of federal law uncovered in the inquiry.

Mr. Silverman has, properly, declined to discuss the scope of his investigations. It will be a disservice both to Mr. Donovan and the public, however, if the special prosecutor's investigations do not provide a full airing of all the allegations that have now been made--the 18 charges addressed at the confirmation hearings, the additional matters that came to light last summer and fall and the most recent disclosures. The Schiavone company--of which Mr. Donovan was part-owner and executive vice president in charge of labor relations and other management matters--was, by Mr. Donovan's own testimony, a closely run operation. The inquiry should properly include all matters relevant to the firm's activities, not just those to which Mr. Donovan is specifically linked.

The special prosecutor's responsibility is not to the Justice Department or to the administration but to the public. His mission is to examine the full range of evidence to determine if it supports a prosecution for a federal offense. His report should also provide a full basis for addressing the further question of Mr. Donovan's fitness for his high office.