In an interview with TV Republika broadcaster, Duda explained that no pressure from "international organisations, various lobby groups, but also some European countries" could change the issue of equal marriage in Poland.
"I do not think that the political majority today would agree to any amendment to the Constitution in this area, water down this clause and open interpretation that marriage could also include other genders,"he said.
"I unequivocally repeat: marriage in accordance with the Polish Constitution is a union between a man and a woman."
Poland currently prohibits marriage for same-sex couples as well as civil unions. In addition, the country is governed by the conservative party called "PiS".