The European Commission has said it would take the unprecedented step of tapping into EU funding earmarked for Poland to collect a fine imposed for refusing to close a coal mine.
The issue is one of several points of friction between the European Union and the eastern European nation.
EU Commission spokesman Balazs Ujvari said the EU had informed Poland of its decision, which will be carried out next week.
Polish government spokesman Piotr Muller said Poland would use "all possible legal means to appeal against this," Poland's PAP news agency reported.
The cut will amount to nearly €15 million for the period between 20 September and 19 October last year.
The total unpaid fine amounts to around €70m including interest, according to an AFP calculation.
The row is the latest to afflict relations between Brussels and one of the EU's biggest members, already on a knife edge over controversial judicial reforms enacted by Poland's conservative government.
The Court of Justice of the European Union hit Poland with the €500,000 a day fine last September for refusing to comply with an order to close its Turow mine producing lignite, or brown coal.
Poland's neighbours, the Czech Republic and Germany, had complained of environmental damage from the mine, including groundwater pollution as well as dust and noise.
Last week, Poland signed a deal with the Czech Republic to end the dispute over the mine, which was confirmed by the court.
But that did not erase the fine, which Warsaw has insisted it will not pay.
Poland argues that decisions taken by the EU court violate the country's right to ensure its energy supply.
However the EU justice commissioner, Didier Reynders, insisted that the European Commission - the guardian of the EU treaties - must be seen to uphold the decisions of the EU court.
"If the member state does not pay, it is obvious that we must organise, as we have said from the start, the withholding of funds," he said.
"If we don't do this, no one would pay their fines anymore, obviously," he said.
Mr Ujvari said the levied amount covering the period September 20 to October 19 would be recovered from Poland's EU funding. That comes to €14.5m plus interest, which takes it close to a total of €15m.
Poland has been hit with another CJEU fine, of €1m per day, for refusing to suspend a national Supreme Court chamber contested by Brussels.
The EU accuses Warsaw of undermining judicial independence and rolling back democratic norms.
There, too, the commission has warned it will recover the fine amount - currently over €100m - from Poland's EU funding if it goes unpaid.
Poland's President Andrzej Duda has proposed a law to scrap the Supreme Court chamber in hopes of drawing a line under the dispute.
The changes still have to be approved by Polish politicians, and legal observers queried whether it is merely a rebranding exercise.
The Polish government was also taken to task by the European Court of Human Rights, a continent-wide body that rules on alleged violations of the European Convention on Human Rights.
The court demanded that Poland guarantee a "fair trial" to a Supreme Court judge critical of the country's judicial reforms, Wlodzimierz Wrobel, who is targeted by disciplinary proceedings.
Poland's populist government insists its reforms are needed for the judiciary to root out corruption and the legacy of judges appointed while the country was still under communist rule.
On the Turow mine deal with the Czech Republic, Poland has agreed to pay the Czechs €45m in compensation in return for Prague withdrawing its complaint.
The European Court of Justice tweeted confirmation that it had closed the case "following an amicable agreement between the Czech Republic and Poland".
Poland is reluctant to close the mine as it feeds a power station that provides around seven percent of the country's electricity needs.
Poland relies on coal to meet up to 80% of its energy, but has vowed to develop green energy sources and to shut its last mine by 2049, in line with EU emissions targets.
