"We must not back down. We must not be soft. We must not give without asking anything in return because it always ends badly," Kaczynski told a PiS convention in the Polish city of Bialystok.
Kaczynski, who stepped down as deputy prime minister in June to focus on next year's legislative polls, said that Poland needed to firmly defend its interests.
Ties between the neighbors have been strained since Poland said that money paid for damage it suffered during the Nazi occupation was not enough. Polish officials lay claims to hundreds of billions of euros in wartime damages, depending on who is counting.
Germany has repeatedly said that it does not believe it owes Poland any more money. It has argued that Warsaw relinquished its right for any further demands under their 1953 deal.