The Polish leadership did not, however, take into account of Mr. Michnik and his refusal to negotiate with a Government he considers illegitimate over an arrest he considers groundless.

Some of his thoughts were in his most recent letter sent out of Mokotow Prison. Published June 7 in Mass Weekly, an underground publication, it refers to the local elections of June 17, which the authorities sought to portray as a step toward democracy.

''Before elections were to be held, the Communists tried to involve me personally,'' Mr. Michnik said in the letter. ''They decided to set free the 11 prisoners, people kept in cells for two and a half years under false accusations, if we would agree to give up political activity for another two and a half years or leave Poland.

''Since I have not authorized anyone to be a mediator in my relations with the wardens, since, being a prisoner, I do not feel myself called on to take part in any negotiations, since my freedom cannot be subject to any bargains, and since I want a trial where I can prove my innocence, I refused any part in the discussions. My friends responded in the same way, rejecting the possibility of buying their freedom for the price of a capitulation.''

Prisoners Spurned Bid To Meet a U.N. Official

Mr. Michnik went on to describe an attempt in which the four were invited to meet with a United Nations official to consider a compromise.

According to people close to the prisoners, the compromise would have allowed them to go abroad for a year, with a United Nations guarantee of their right to return to Poland. Unlike his co-defendants, Mr. Michnik refused to see the official.