But Jarosław Kaczyński, whose governing conservative Law and Justice (PiS) is seeking a second term in power in a ballot on Sunday, insisted that his party champions freedom, tolerance and democracy.
Law and Justice strongly supports traditional values, a stance that has helped it win support in a country which is overwhelmingly Roman Catholic.
Kaczyński told an election convention in Warsaw on Tuesday that European civilisation has always been based on Christianity.
"This civilisation is under attack from some west of our borders and we have to defend ourselves here," Kaczyński told supporters.
He added: "There is a difference between tolerance and affirmation … There will be no homosexual marriages; there will be no adoption of children [by gay couples]; there will be no euthanasia either. We have to defend ourselves against these."
Kaczyński claimed that his party’s arch-rival, the opposition Civic Coalition grouping, wants to deprive Poles of freedom of religion and to enforce political correctness through legal penalties.
"A PiS government is a government of freedom in all areas, a government of freedom, tolerance and democracy," Kaczyński added.
Poles will head to the ballot box to vote in parliamentary elections on Sunday and will elect 460 MPs and 100 senators for a four-year term.
The country’s ruling conservatives appear to be running ahead of an opposition divided into separate blocs, according to the latest polls.