During his visit to Warsaw to testify before a parliamentary scam investigation panel, Tusk, a Polish national, urged Poland's ruling Law and Justice Party (PiS) to "come to their senses" regarding Poland's place within the EU, saying that their current political course might end up with Poland being expelled from the union.
"It does not matter to me whether [PiS leader] Jaroslaw Kaczynski plans to leave the EU or just initiates some processes that lead to that outcome," Tusk, a long-time critic of the Eurosceptic PiS, told reporters during his visit.
"The issue is that [former UK Prime Minister David] Cameron also had no plan to take the UK out of the EU. And the will [among member states] to keep Poland inside the EU is smaller than the will to keep the UK in it," Tusk said. It was Cameron who called the 2016 referendum that launched the beginning of the Brexit processes.
"This issue is incredibly serious. The risk is deadly serious. I want everybody to come to their senses," he added, according to Reuters.
Last month, ahead of local elections, Polish Justice Minister Zbigniew Ziobro asked the country's constitutional court to check whether EU law was compatible with the Polish constitution, Reuters reports.
Some say this inquiry triggered "anger" among Polish voters, which led to PiS' limited success in local elections. Speaking to journalists, Tusk also commented on this, saying the results serve as a "big warning" for the party.
Tusk himself was prime minister of Poland between 2007 and 2014. During his time, the Amber Gold financial pyramid scheme unraveled, cheating thousands of Poles out of their money. During his trip to Warsaw, Tusk was questioned by a parliamentary investigation commission on whether he was aware of the scam while it was ongoing and why the government did not react in time, the Independent reports.
Speaking to reporters, Tusk declined to say whether he would return to domestic politics in Poland once his EU mandate expires in 2019.