Tusk, who was Poland's liberal premier at the time of the crash, told reporters he "had no doubt" he was being attacked by his arch-rival Jaroslaw Kaczynski -- the powerful leader of Poland's governing rightwing populist Law and Justice (PiS) party -- but vowed he would not be intimidated.
Addressing concerns over recent moves by the PiS that have set Warsaw on a collision course with the EU over possible rule of law violations, Tusk also warned that "Poland's future in the Europe is today being called into question."
Tusk shot back: "I have nothing to fear and Mr Kaczynski can't scare me regardless of his determination in attacking me."
Kaczynski unleashed an emotional diatribe in parliament two weeks ago, accusing Tusk's former liberal Civic Platform (PO) party of being responsible for the Smolensk crash that claimed the life of his twin brother, the then president Lech Kaczynski.
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"Don't wipe your treacherous mouths with my late brother's name. You destroyed him, you murdered him, you are scoundrels," Jaroslaw Kaczynski told PO deputies.
Polish and Russian investigators found that pilot error, bad weather and poor air-traffic control were to blame for the accident.
"This tragedy should not be exploited for political purposes, nor should the law be used as a hammer against the opposition or rivals," Tusk told reporters after being questioned by prosecutors.
"I can't rule out any (future) scenario. What I see in Mr Kaczynski's eyes... Is a kind of passion focused on attacking me.
"The entire context of the case is of course political. I have no doubt about it, but I have nothing against the prosecutors who questioned me," Tusk added.
Tusk already testified for eight hours in Warsaw in April as a witness in an investigation of two former military counter-intelligence chiefs accused of overstepping their duties in the initial investigation of the crash.
After taking power in late 2015, the PiS launched a fresh probe into the crash that also killed a number of senior Polish officials and a commission of enquiry it controls suggested in April that an explosion likely caused the aircraft to break up in the air.
The crash occurred as the presidential delegation was heading to a commemoration in Russia's Katyn forest for thousands of Polish army officers killed by Soviet secret police in 1940 -- a massacre the Kremlin denied until 1990.
The European Union announced Saturday it had launched legal action against Poland's PiS government over new court reforms that it fears will erode judicial independence.
Tusk said today in Warsaw that the PiS law "confirms that Jaroslaw Kaczynski is dreaming of a justice system that will answer to him."
The EU chief also issued a stark warning about the PiS government's decision to ignore a ban imposed last week by the EU's top court -- the European Court of Justice -- on logging in the Bialowieza forest, Europe's last primeval woodland.
I believe that would be one of the most dangerous moments in our history. I'm afraid we're closer, rather than farther away, from that moment.
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