The case, known as the "two towers" affair, centred on a never-built pair of skyscrapers planned for a plot in Warsaw owned by Srebrna, a company linked to PiS.
Austrian businessman Gerald Birgfellner had accused people acting on the firm's behalf of misleading him over the project between 2017 and 2018, causing him losses of at least EUR 1.3 million.
The Warsaw District Prosecutor's Office said on Tuesday it had closed the case on 25 June, finding that the actions in question did not constitute a criminal offence.
Spokesman Piotr Skiba said the office would withhold detailed reasoning until the decision is translated into German for Birgfellner.
The investigation, opened in February 2025, also examined separate bribery allegations involving a member of the board of the Lech Kaczyński Institute, the foundation linked to Srebrna, including a claim that Birgfellner had been encouraged to pay PLN 100,000 (EUR 23,270) to secure favourable treatment.
Prosecutors said none of those allegations met the threshold for a crime either.
Roman Giertych, Birgfellner's lawyer, said he would appeal, accusing the prosecutor leading the case, Małgorzata Szeroczyńska, of bias.
"[She] today, as I expected given that 80 percent of my questions to Jarosław Kaczyński were blocked, dropped the investigation into the two towers," he said.
Giertych also criticised the removal of the original investigator, Ewa Wrzosek, from the case last year, arguing that prosecutors sidelined her after PiS used the death of Barbara Skrzypek to accuse Wrzosek and Birgfellner's legal team.
Skrzypek, a longtime Kaczyński aide, was questioned as a witness in the probe in March 2025 and passed away days later.
A separate investigation into her death found no third-party involvement, concluding she died of a heart attack unrelated to the stress of questioning.
Wrzosek, now delegated to the justice ministry, pushed back on the prosecution's office over the delayed explanation, saying there was no legal requirement to provide victims with translations of decisions.
"In an ideal world, every victim who does not speak Polish should receive a translation," she wrote on X, but added this rarely happens "simply because there is no money for it."
Giertych responded that no translation had been requested and that lawyers had not even received the written decision yet, relying instead on the prosecutors' public statement.
Kaczyński himself was questioned as a witness in the case in early June, answering over several hours without invoking his right to silence.
(ał)
Source: PAP