Mr Oleksy has consistently denied the allegations, levelled by Poland's security service and announced to parliament in December by the outgoing interior minister, Andrzej Milczanowski, who said the security service (UOP) had evidence Mr Oleksy knowingly informed for foreign intelligence since before the 1989 fall of Communism until last year, when he was speaker of parliament. It later emerged Mr Milczanowski meant Soviet and Russian spies.
Mr Oleksy, once a senior Communist, quit as prime minister when the prosecutors launched a three-month investigation on 24 January, which they had to complete this week.
The furore shook the ruling coalition of Mr Oleksy's ex-Communist Democratic Left Alliance (SLD) and the Polish Peasant party, which only after tough negotiations formed a reshuffled cabinet under the SLD's Wlodzimierz Cimoszewicz. The affair broke just before the former president Lech Walesa, once the Solidarity union leader, handed over to his ex-Communist opponent Aleksander Kwasniewski, who had narrowly beaten him in November elections.
Mr Oleksy dubbed the allegations a "filthy provocation" by pro-Walesa UOP officers, admitting only to an innocent acquaintance with Vladimir Alganov, a Warsaw-based Moscow diplomat, who later proved to be an intelligence officer. He and his successor at Russia's Warsaw embassy were also named in the prosecutor's investigation, but Mr Gorzkiewicz said no action would be taken against them either.
Parliamentary elections are due next year and Walesa is trying to rally the centre-right opposition for a comeback. He attributed the outcome of the inquiry to expediency by the ex-Communists. "The political option in power was unable to do anything else with such an important problem. We will return to this matter after the parliamentary elections."
The SLD's core Social Democratic (SdRP) party made Mr Oleksy its leader after his resignation in a show of solidarity and confidence in his innocence. He refused to comment yesterday but the decision was clearly a relief.
The SdRP deputy leader, Izabella Sierakowska, said that the party would push for Mr Milczanowski and others involved in bringing the allegations to be tried before a special state tribunal. "I think that in the nearest future. . . those who are guilty should be punished," she said.