ONE OF OUR MOST vigilant critics, Accuracy in Media, Inc., took out an advertisement in this paper last Friday to denounce a recent news story from Havana. In the ad AIM's chairman, Reed Irvine, argued that The Post should have identified the author of that story, Lionel Martin, as a former employee of the Cuban government and contributor to a left-wing weekly, the Guardian. Mr. Irvine had made that point earlier in a letter to the editor that we declined to run on grounds that it was an ad hominem attack. It impugned a news dispatch and its author, not by demonstrating any inaccuracy in the dispatch itself, but by selectively reciting only a part of the writer's personal and professional background.We pursue the matter here, For Your Information, because we consider it useful to discuss with our readers, from time to time, the nature of our business and the conditions under which it is conducted.

Mr. Martin first enterd the news business as a broadcaster for the Pacifica Foundation's radio station in Berkeley, Cal. In 1961 he went to Cuba, where he has spent most of his career. For some years he worked for the Ministry of Education, and began free-lancing. In recent years he has written for several major newspapers and television networks in this country and Canada. Since June he has been an occasional correspondent for The Post - in the language of the trade, a stringer.

A stringer typically serves a number of clients and is paid by the article, and also sometimes with a modest monthly "retainer." Also typically, his career is buil on long acquaintance with the country or region that he covers. In contrast, a newspaper's staff correspondents have the job security of full-time employees and move around with their changing assignments.

A country like Cuba warrants careful news coverage, but not a permanently assigned staff correspondent. The Post's editors try to strike a balance. The staff correspondents, on reporting trips through the country, have great freedom to write, but they lack the background that comes only through living there. The residnt stringer commands that background, but writes under political constraints.

Constraints on writers are nothing new, but in the Third World they are becoming more severe. Governments of every political denomination are becoming increasingly sensitive to the news of them that appears in the American and European press. One ready weapon in a government's hands is the threat to expel the offending journalist. For a stringer, expulsion is an extremely serious matter, cutting him off from the subject that has been his livelihood and his career. It is up to a newspaper's editors to keep in mind the inhibitions under which a stringers works, particularly in a country with a highly ideological and authoritarian government like Cuba's,

The specific news story to which AIM objected appeared in this paper Dec. 2 under the headline "Will Influx of Capitalist Tourists Bring Back the Vices of the Old Regime?" Without, in fact, even referring to "capitalism" in his dispatch, Mr. Martin reported a rise in prostitution in Havana, and the government's trade. AIM took the article to ba a left-wing attack on capitalism. We, in contrast, consider it to be straight-forward reporting of a genuine concern within Cuba as it slowly reopens itself to Western tourists.

What if a writer offered a news story that seemed to The Post's editors to be biased or inaccurate?We would decline to print it. Editors here make that decision dozens of times every day. To our readers we offer the principle that the character of our coverage is formed not by the personal histories of our contributors abroad, but by the judgment of our editors here in Washington. The ultimate test, of course, is in the final product, which is entirely available, every day, for your careful inspection.