Poland's independent Solidarity trade union federation and the Foreign Ministry today strongly denied stories written by an American who said he was a free-lance writer and who described what he called a secret underground network here ready to resist Soviet invasion.

The stories were written on the basis of a four-week trip to Poland by a former exchange student in Poland, Harley Lippman, 26, formerly of Merrick, L.I., and now a resident of Boston, where he said he is director of the Jewish Labor Committee.

Various versions were circulated by several U.S. news organizations and broadcast during Lippman's appearance an ABC's "Good Morning America" show. The New York Times Co.'s Syndication Sales Corp. also distributed two of the stories, which appeared in one combined version in The Times of London entitled "On the Run in Poland With My Friends in Solidarity."

Janusz Onyskiewicz, Solidarity's press spokesman, described the Lippman articles as they appeared in the London newspaper as untrue. He said they depicted Solidarity, which is a legally recognized union organization in Poland, as if it were an underground movement operating in conditions similar to World War II.

In response to queries, the press department of the Polish Foreign Ministry described the Lippman articles as "an insult to serious journalism." m

Lech Zembrzuski, an official in the department, said: "These articles were damaging to this country and damaging to Solidarity. We're not surprised when something like this appears in the tabloid press, but we don't expect it from serious newspapers such as the London Times and The New York Times."

The 2,000-word story appeared in The Times of London on May 11. It was copyrighted "New York Times."

[Walter E. Mattson, president of The New York Times Co., issued a statement in New York saying: "A report on Poland's Solidarity movement, written by a free-lance author and distributed by The New York Times Co.'s Sundication Sales Corp., appears to be of questionable accuracy. The articles written by Harley Lippman, were distributed under his copyright. They were not published by The New York Times, and were not seen by Times editors. Syndication Sales Corp. is an independent business operation of The New York Times Co., and has no relationship with the news operation of The Times newspaper. We are deeply concerned by this event. We apologize to the editors of the publications that ran the Lippman article. Syndication sales will no longer handle such free-lance material."]

During his stay in Poland in February, officials say that Lippman described himself variously as an emissary of the AFL-CIO, a representative of Sen. Edward Kennedy [D-Mass.] and a correspondent of The Washington Post.

Lippman wrote that he spent 27 days being smuggled by Solidarity activists "through a bewildering array of safe houses and secret rendezvous points" to avoid arrest by police. He said he spent "every waking moment" of a week with Solidarity leader Lech Walesa in his Gdansk apartment, sharing a room with Walesa's eldest son, 10-year-old Bogdan, and babysitting while the Polish labor leader went out with his wife.

This claim has been strongly denied by Walesa and Solidarity. According to Onyskiewicz, "it is totally untrue, as are other statements which may give a false impression that Mr. Lippman is Mr. Walesa's friend."

Lippman also wrote that he was taken blindfolded to interview Polish soldiers and officers planning to fight in the event of a Soviet invasion. He described one such alleged encounter with an anonymous Army general -- "stocky, clean-shaven, and short-haired" -- in a forest in central Poland.

Reached by telephone in his Boston office, Lippman ssid, "I stand by my story."

He said the denials from Poland could be attributed to reluctance to be identified with him and what he wrote because, he said, he was strongly identified with "Zionist activities" and a "hard-line" position on the Soviet union.

"Solidarity has to deny this, which I understand," he added. "The reason there is such a strong reaction to this is that they feel that I am a provocation . . . They feel that I misrepresented Solidarity. I understand that."

In contrast to the impression made by his story, Lippman said the groups he descibed as moving him underground from safe house to safe house were not representative of the Solidarity trade union movement.

"It is accurate to say this is not Solidarity," he went on. "It is a small group of people. The people who showed my around are one fraction of the militants. Some people are members; some people are not."

[Lippman insisted, however, that he had spent a week living with Walesa, whom he said he met during a stay as a student in Poland in 1975-77, and added that he had photos depicting him going to mass with Walesa and playing with his children.]

The central theme of Lippman's articles in The Times of London is that he spent "27 days underground, being shuttled -- usually at night -- the length and breadth of Poland." He went on: "My friends fitted me out in Polish clothes so I could blend witht he people. I slept in the homes of strangers who invariably treated me as a comrade simply because Solidarity had sent me."

This claim conflicts with the accounts of Polish officials and Western journalists who remember Lippman's stay in Poland as open. At a meeting of Polish journalist, for example, he was described as a writer for The Washington Post who would be pleased to offer help and advice.

He also had a meeting with Poland's deputy foreign minister, Marian Dobrosielski, on the basis of a letter of introduction from Sen. Kennedy. Foreign Ministry officials said Lippman introduced himself to Solidarity in Gdansk as from the AFL-CIO.

The organization has denied that he was their representative. A spokesman for Kennedy's office confirmed that Kennedy wrote a routine letter introducing Lippman as a constituent of his.

[Lippman, in the telephone conversation, described the identifications with The Washington Post and the AFL-CIO as mistakes due to imprecise translations and Poles' misunderstanding of his lack of specific affiliation.]