The panel on Wednesday released its preliminary findings, stating that the former Polish prime minister claimed not to recall specific instances of such cooperation when questioned by prosecutors in 2017.
State broadcaster TVP Info reported that "on some dozen occasions" during questioning, Tusk declared that he did not remember or was not aware of any cooperation between Poland's Military Counterintelligence Service (SKW) and Russia's Federal Security Service (FSB) during his time as prime minister.
Tusk, who leads the opposition liberal Civic Coalition (KO), told prosecutors that relevant information was contained in government documents from the time, according to TVP Info.
The broadcaster said a recent documentary showed that Tusk in those days signed a Polish-Russian security cooperation agreement that "was not consulted with NATO."
Sławomir Cenckiewicz, the head of the state commission into Russian influence on Poland's internal security from 2007 to 2022, said in a television interview on Thursday that "there were many documents" confirming links between Poland's SKW and Russia's FSB when Tusk was prime minister, the niezalezna.pl website reported.
Cenckiewicz produced a 2011 document in which he said the then head of Poland's SKW invited the director of Russia's FSB to Poland "to discuss future cooperation" between the Polish and Russian agencies.
In its preliminary report, the commission recommended that Tusk and senior ministers in his Cabinet at the time "should not be appointed to positions with responsibility for national security."
Tusk, a former top European Union official and Poland's current opposition leader, who is likely to be elected the country's next head of government, said the creation of the panel had been "politically motivated" and the commission's report "proves this," state news agency PAP reported.
On Wednesday night, Polish lawmakers voted to dismiss the members of the commission into Russian influence, including Cenckiewicz.
The move was backed by MPs from Tusk's Civic Platform (PO) party, the rural-based Polish People's Party (PSL), the centre-right Poland 2050 group, the Left party, and some lawmakers with the far-right Confederation group, news outlets reported.
The commission had been appointed by the previous parliament, controlled by the ruling conservative Law and Justice (PiS) party.
Government spokesman Piotr Müller said the MPs' vote on Wednesday had been "motivated by fear," the wpolityce.pl reported.
Tusk was Poland's prime minister from 2007 to 2014.
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Source: TVP Info, niezalezna.pl, PAP, wpolityce.pl