Poland could officially demand reparations from Germany for the 6.2 trillion zlotys ($1.32 trillion) it counts as losses from the Second World War.
The ruling nationalist Law and Justice (PiS) party said on Thursday it would seek further recompense, despite Berlin having said all financial claims have been previously settled.
Poland's new estimate tops the $850 billion estimate by a ruling party lawmaker from 2019 - and party leader Jaroslaw Kaczynski has given its strongest indication yet it would take action.
"The sum that was presented was adopted using the most limited, conservative method, it would be possible to increase it," he said.
The combative stance towards Germany, often used by PiS to mobilize its constituency, has strained relations with Berlin. It intensified after Russia invaded Ukraine amid criticism of Berlin's dependence on Russian gas and its slowness in helping Kyiv.
Some six million Poles, including three million Polish Jews, were killed during the war and Warsaw was razed to the ground following a 1944 uprising in which about 200,000 civilians died.
In 1953 Poland's then-communist rulers relinquished all claims to war reparations under pressure from the Soviet Union, which wanted to free East Germany, also a Soviet satellite, from any liabilities. PiS says that agreement is invalid because Poland was unable to negotiate fair compensation.
"The German government's position is unchanged: the reparations question is closed," a German foreign office spokesperson said. "Poland renounced further reparations a long time ago, in 1953, and has since repeatedly confirmed this."
Donald Tusk, leader of Poland's biggest opposition party Civic Platform, said on Thursday that Kaczynski's announcement was "not about reparations".
"It's about an internal political campaign to rebuild support for the ruling party," he said.
PiS is still leading in most opinion polls but its edge over civic platform has narrowed in recent months amid criticism of its handling of surging inflation and an economic slowdown.