WARSAW, Poland (AP) _ Solidarity leader Lech Walesa said today the convictions of four secret police officers in the murder of a Roman Catholic priest should be a starting point for a new dialogue between the Communist government and the people. But he said he continued to fear ''for the future.''

After the verdicts were announced Thursday, another Roman Catholic priest, the Rev. Antoni Lewek, urged worshipers gathered at the church where the slain priest had preached to prepare for an ''ideological battle.''

The Rev. Jerzy Popieluszko was abducted on a highway near Torun, in northern Poland, on Oct. 19, and his body was found bound, gagged and severely beaten, in a reservoir of the Vistula River 11 days later.

After a six-week trial, the five trial judges sentenced two of the defendants to 25 years in prison - the most severe penalty in Poland short of execution by hanging.

Walesa's statement, read over the telephone by assistant Henryka Kinaszewska from the southern skiing resort of Zakopane where Walesa was vacationing, was the 1983 Nobel Peace Prize winner's first public reaction to the verdicts.

''We would like to recognize this trial as a sign of the good will of the authorities toward accord, of the advantage of the force of law over the right of force,'' Walesa said. ''But new facts occurred that make us doubt it.''

He cited the government's decision not to allow prominent Solidarity activist Seweryn Blumsztajn to return to Poland on Tuesday from three years exile in France. Police stopped Blumsztajn at Warsaw airport and put him on a return flight to Paris on the grounds that he carried an improper passport.

''There is a need for forgiveness, but there is also a need for results in the struggle against evil,'' Walesa said. ''If this doesn't happen, the chance created by the trial will be missed.''

''In the end the trial didn't alleviate our fears for the future,'' Walesa said. ''Let's not forget that a Polish priest was killed by the functionaries of the state authorities.''

Chief Judge Artur Kujawa told the court Thursday that the defendants ''soiled the good name of the Polish People's Republic. They put in shame the state's political system.''

Kujawa's remarks were broadcast in full by state radio and television.

Col. Adam Pietruszka, the highest-ranking Interior Ministry official charged in the killing, received a 25-year prison sentence for aiding and abetting his three subordinates.

''Pietruszka's aid was a necessary condition for the success of the whole operation,'' Kujawa said.

The court convicted Capt. Grzegorz Piotrowski of kidnapping and murdering the priest and sentenced him to 25 years in jail, rejecting a prosecution request for the death sentence.

Piotrowski's two subordinates, Lts. Leszek Pekala and Waldemar Chmielewski, were found guilty of murder but received lighter prison terms because they were the ''victims of actions by their superiors,'' in the words of the court. Pekala was sentenced to 15 years; Chmielewski, 14.

More than 1,500 people gathered for a Mass Thursday evening at St. Stanislaw Kostka Church in Warsaw where Popieluszko's monthly sermons used to draw thousands of Solidarity sympathizers.

Lewek told the faithful that the trial was a ''painful and emotional'' experience for all Polish Catholics because of the attacks against Popieluszko made by the government prosecutor.

''We must be ready for an ideological battle,'' Lewek said. ''Not a battle with the use of sticks but with words and truth.''

Poland's population of 33 million is predominantly Roman Catholic.

During the trial, the prosecutor had depicted Popieluszko as an extremist whose anti-government activities angered and frustrated Interior Ministry officers.

A spokesman at the Roman Catholic episcopate headquarters in Warsaw said there would be no official reaction from the church hierarchy until after a meeting of the country's bishops next week.

But the spokesman, the Rev. Henryk Brunka did say: ''The church is not going to criticize it (the verdict) as too high or too low. ... In the case of a 25-year penalty a man has a lot of time to think about himself and about others.''