European Council chief Donald Tusk on Saturday joined thousands at a pro-Europe opposition rally in Warsaw, calling on his fellow Poles to vote against the eurosceptic governing conservatives in this month's EU elections.
"You have no choice... You can't leave the future of our children and grandchildren in their hands," Tusk said, referring to the right-wing Law and Justice (PiS) party.
"Our children and grandchildren would never forgive us... Go forth towards victory," he added to cheers and applause at the rally organised by the opposition European Coalition.
A former Polish premier, Tusk is widely believed to be eyeing a political comeback at home once his EU term ends in November.
Without referring to him by name, Tusk compared his arch-rival and PiS leader Jaroslaw Kaczynski to an ayatollah during the rally attended by Poles from across the country.
Marching through downtown Warsaw with Polish and EU flags, participants chanted "We will win" and "Freedom, equality, democracy". Some held up signs with slogans like "We want Europe".
One poster read "Duck off" in an allusion to Kaczynski, whose last name is similar to the Polish word for duck.
"Those currently in power are against values that I hold dear," said student Aleksander Jaszczynski.
"We want Poland's voice to be modern, European, tolerant and open-minded," he told AFP.
Computer scientist Miroslaw Janusz said he attended the rally to back a Poland that plays a positive role in the EU instead of "turning its back on the bloc, like the current government."
The PiS, which has frequently sparred with Brussels since coming to power in 2015, has toned down its Euroscepticism ahead of the May 26 EU ballot and the Polish general election later this year.
The party also recently announced plans to raise prison terms for paedophilia after a documentary on child sex abuse by Polish clergy sent shock waves through the devout country of 38 million people.
Observers say the film could deal a blow to the chances of the ruling conservatives in the election, given their close ties to the Catholic Church.
The PiS and Poland's other main political force -- the European Coalition, a group of opposition parties led by the liberal Civic Platform (PO) -- are currently polling neck and neck, with the new progressive Spring party in third place.
'You have no choice... You can't leave the future of our children and grandchildren in their hands,' Tusk said, referring to the right-wing Law and Justice (PiS) party.