Speaking in parliament, Tusk condemned recent comments by opposition lawmakers that criticised the presence of Ukrainians in public institutions and questioned the role of officials of Ukrainian descent in government.
"If origin, race or skin colour begin to determine a person's place in public life, then you, too, will become victims of that wave if it is not stopped," Tusk told opposition lawmakers.
The remarks came a day after opposition politicians attacked Deputy Science Minister Andrzej Szeptycki over comments comparing members of the World War II-era Ukrainian Insurgent Army (UPA) to Poland's postwar anti-communist resistance fighters.
The UPA remains a highly sensitive subject in relations between Warsaw and Kyiv because of wartime massacres of Polish civilians by Ukrainian nationalists in the Volhynia and eastern Galicia regions of what was then German-occupied Poland.
During Wednesday's parliamentary debate, senior opposition politician Przemysław Czarnek, the Law and Justice (PiS) party's nominee for prime minister in the next election, accused the government of betraying Poland's interests and demanded an explanation for why "Ukrainians insulting Poles" remained in government.
Right-wing lawmaker Janusz Kowalski announced plans to investigate what he described as the "Ukrainianisation" of Poland's public administration.
'Such witch hunts usually ended in catastrophe'
Tusk said such rhetoric echoed dangerous trends that had repeatedly led to tragedy in European history.
"I am talking about a kind of witch hunt," he said. "We have witnessed such witch hunts many times in Europe over the past 150 years. They usually ended in catastrophe."
The prime minister also referred to remarks made last year by nationalist activist Robert Bąkiewicz, who called for "weeds" to be "uprooted from Polish soil," arguing that increasingly hostile rhetoric toward Ukrainians was part of a broader and troubling pattern.
According to Tusk, inflammatory statements by political leaders encourage wider social hostility toward people of different backgrounds and views.
He argued that Poland's strength has historically come from its diversity and warned against defining patriotism through ethnic purity.
"As a historian, I cannot fail to mention that among the figures who shaped Polish history were people such as Copernicus, Chopin, Kościuszko and Piłsudski," Tusk said, referring to prominent Poles with diverse family backgrounds.
'There is still time to stop'
The prime minister cited the rise of the Solidarity movement in the 1980s and the public response to Russia's invasion of Ukraine in 2022 as examples of national unity that enhanced Poland's international standing and security.
"When Poland showed solidarity, it showed the best face of politics imaginable," Tusk said. "Poles who do not turn against one another and do not search for ethnic enemies build the strength of the country."
He urged opposition lawmakers to abandon divisive rhetoric before it escalates further.
"The worst catastrophes began with words, then incidents, and then waves of hatred," Tusk said.
"There is still time to stop," he added.
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Source: TVP Info, IAR, PAP