WARSAW, Poland (AP) -- Poland's electoral authority said Thursday that the former governing nationalist conservative party violated campaign funding rules in the 2023 parliamentary vote, and imposed a penalty worth millions of dollars that would undercut the party's resources for next year's presidential election.

The State Electoral Commission said that the campaign of the Law and Justice party, which led Poland from 2015-2023 and is now the main opposition force, improperly took 3.6 million zlotys ($930,000) in public money.

The commission ordered the conservative party to pay back that amount, and it also ordered a cut in the party's government subsidies for the coming years, amounting to about 10 million zlotys ($2.5 million ) per year.

The commission's decision can be appealed to the Supreme Court, where Law and Justice still holds some sway. The court's verdict would be binding and final.

Prime Minister Donald Tusk posted on X that the party was now "learning the true meaning of the words law and justice."

The penalties would significantly reduce the party's resources for the 2025 presidential election, in which it will seek to maintain its control of that office.

Mateusz Morawiecki, who served as Law and Justice prime minister, said the decision was "shameful" and was part of a "political game of the current government whose goal is revenge and pushing the opposition to the margin."

He said the government wants to weaken Law and Justice before the presidential election, and that the party would appeal the decision to the Supreme Court.

Earlier this month, party leader Jaroslaw Kaczynski said that the commission was acting under pressure from Tusk's centrist and pro-European Union government. Kaczynski said that any punitive decision would spell the end of democracy in Poland.

The electoral commission is obliged by law to review the financial reports of all parties that ran in an election, and any funds exceeding the party's budget by more than 1% must be returned and a fine is imposed. It pointed to Law and Justice campaigning during summer military picnics for the general public and to Justice Ministry television spots as examples of using public funds for election purposes.

The euroskeptic Law and Justice party, which had put Poland on a collision course with Brussels over its violations of the rule of law, was the biggest single vote-getter in the Oct. 15 general election, but a coalition led by Tusk won a comfortable majority of seats in parliament, removing the conservatives from power.

Ever since, the government has been investigating its predecessor on accusations of abusing power and state finances. Kaczynski and his supporters call the efforts a politically motivated attempt to undermine the opposition.