The long evolution of the American newspaper from political prostitute to monopolistic public utility has produced within the industry a modern ethos that emphasizes such intellectual virtues as honesty, fairness and devotion to "truth." Lying, venality, bigotry and conscious distortion of the news are generally proscribed.

But the practices of journalism frequently are at odds with its rhetoric; its ethical principles often prove to be of the situational variety. The principles of detachment and "impartiality," for example, are constantly at risk in the relationships that arise between journalists and their sources. Mutual exploitation is a common result. For the journalist, the payoff may be snippets of "insider" information or even a major disclosure. For the supplier of these "leaks" the journalist may be the tool for image enhancement, for the achievement of a policy objective or for the scuttling of an adversary.

Richard Nixon rose to national prominence in the late 1940s through his labors on the House Committee on Un-American Activities in pursuit of Alger Hiss and his ties to the Communist Party. Throughout that investigation, one of Mr. Nixon's principal tutors, strategists and defenders was Bert Andrews, the Washington bureau chief of the New York Herald Tribune and a one-time friend of Mr. Hiss. Needless to say, Mr. Andrews and his newspaper were in command of the story.

Clark Mollenhoff, a Washington correspondent for the Des Moines Register in the 1950s and '60s closely collaborated with congressional committees in the search for Truman administration tax scandals and in the exposure of corruption in such labor unions as the Teamsters. His reputation as an investigator spread far and wide and earned him many prizes includng the Pulitzer. The political fortunes of some of his collaborators, Robert Kennedy included, were substantially improved.

These political-journalistic productions retain their popularity and mutual profitability. The New York Times recently has been involved in a collaboration with one of the Senate's most partisan exhibitionists, Howard Metzenbaum, the Ohio Democrat. Together they are generating a bountiful harvest of publicity from intersecting investigations of a questionable savings and loan transaction.

The orchestrator of the Metzenbaum inquiry, Brian McTigue, has a particular incentive to succeed. His own reputation was tarnished, and he was dismissed from his congressional job last year for involvement in the unethical taping of a committee witness. His employer at the time was the chairman of the House Energy Committee, Rep. John Dingell (D-Mich.), whose collaborations with journalists are legendary. The latest involves The Wall Street Journal. The target is the Northrop Corp., and the subject is not exactly new. The company has been under investigation for more than a decade for putting defective guidance devices in cruise missiles.

These practices are commonplace, and The Washington Post is no stranger to them. They are not corrupt or unethical per se, but invariably they involve situations in which conflicting interests are present -- those of the hunters and of the hunted. For the newspaper collaborating with either side, the ethical and professional problems are obvious. How do defendants, for example, get fair treatment when the newspaper has a journalistic stake -- perhaps a prize -- in an outcome favorable to congressional committee prosecutors? Can the public be confident that the motives, tactics and procedures of these committees and the evidence itself will be scrutinized with a critical cast of mind? Questions of this sort are especially pertinent because of the star-chamber nature of many congressional investigations and because of the political opportunism of many committee members and their staffs.

There have been times when the behavior of congressional committees was as much a focus of newspaper interest and concern as the behavior of their quarry. This was especially true in the McCarthy era, when intellectuals, writers, artists and journalists were frequent targets of committee investigators.

Today the activities and procedures of Hill committees are non-stories. If they use or misuse their powers to bully witnesses, smear their reputations unfairly and otherwise violate their civil liberties, that is an important story. Let us hope there is someone around prepared to tell it.