he Polish government today refused Pope John Paul's request for an amnesty for political prisoners, but reaffirmed plans to welcome the pontiff here in June.

In a news conference, government spokesman Jerzy Urban also denied a request by Lech Walesa, leader of the banned trade union Solidarity, for talks with the government.

New street clashes erupted this evening in several major Polish cities, including Warsaw, Gdansk and Krakow, as worshipers emerged from masses marking Poland's Constitution Day. Convoys of trucks and police in riot gear were again massed in downtown areas to prevent marches from forming, and water cannons and tear gas reportedly were used in skirmishes as security forces sought to disperse the crowds.

Focusing on the desire of this largely Roman Catholic nation for a second pilgrimage by the Polish-born pontiff, Communist authorities had warned that demonstrations this week might upset planning for the papal visit.

But the government downplayed Sunday's pro-Solidarity rallies, as the minister for religious affairs, Adam Lopatka, told reporters that the disturbances in 20 cities and towns would have "no effect" on preparations for the pope's trip.

Walesa had hoped the showing of worker support for the banned union would bring the Warsaw government to accept his plea for new talks. But Urban, joining Lopatka at a press conference, spurned Walesa's motion in harsh terms.

He described the former union chairman as "a has-been" who lost his chance to strike a deal with the government in 1981.

"He will not be a partner for our government," Urban asserted.

Attacking western news organizations for headlining Walesa's statements and actions, the spokesman added: "This artificial building up of Walesa will lead nowhere." He went on to accuse Walesa of being a "card" that the Reagan administration is playing in its anti-Polish policy.

Urban also rebuffed the insistent petitioning by the Roman Catholic Church for an amnesty for people jailed for martial-law crimes. He said the clemency process now considering political prisoners on a case-by-case basis would cut the number of martial-law violators in jail to "several score" and thus remove the humanitarian basis for an amnesty.

He also stated that a general pardon might be seen as a bending to pressure, and raise dangerous doubts about the Polish government's determination to combat crime.

Lopatka confirmed that the pope, in a letter to the chairman of the Polish Council of State, Henryk Jablonski, personally appealed for an amnesty before his arrival June 16. But the religious affairs minister said the pope's statement on the subject was worded as a request, not as a condition, for the pilgrimage.

Revising earlier figures on the number of cases involved, Urban said that as of the end of March, 3,048 people had been convicted of political crimes since the imposition of martial law in December 1981. Most of these people received suspended sentences, Urban said, and many of those originally imprisoned have since been released either on temporary furloughs or freed under the clemency process started with the suspension of martial law last December.

Urban said 215 people were still in prison for martial-law violations. Some prisoners, he said, were refusing to apply for clemency as an act of political protest, and one inmate even refused to leave jail after receiving clemency.

A senior church official had no quarrel with the government's figures, agreeing that the number of prisoners in question was not that large. But the official stressed that the importance of the church's amnesty appeal centers on the need for the government to demonstrate "a change of attitude toward society."

Their public statements would appear to leave church and state at a standoff on this critical issue. A way out might be found if the government chooses to signal before the pope arrives that certain lenient steps will be taken after the papal visit.

Discussing the May Day disturbances, Urban said 1,000 participants had been detained but many were released after two or three hours. He had no casualty figures for demonstrators and only spotty ones for the police from around the country.

Concerning the one death reported so far--a 29-year-old printer in the steel town of Nowa Huta--Urban said the authorities were still investigating the exact cause. Countering a semi-official account yesterday that the area in which the body had been found had been the scene of street clashes, Urban said no fighting had taken place there and he expressed doubts that the death was related to the melee.

In other remarks, the government spokesman ridiculed a statement Sunday by President Reagan in support of a pro-Solidarity rally in Washington. Saying that only about 50 people participated, Urban said some birthday parties in Poland draw bigger crowds than that. The Washington Post reported Monday that about 100 people attended the rally at Lafayette Square.

Urban attacked Reagan for "political cynicism" for a comment about Poland's weak economic condition in view of U.S. sanctions against the Warsaw government, and he said Washington's "interference" in internal Polish affairs "augurs ill for U.S.-Polish relations" in the future.

Tonight's clashes occurred despite instructions from the Solidarity underground leadership to avoid further confrontations with the authorities in the days leading up to the pope's visit.