German Chancellor Angela Merkel on Tuesday threw her weight behind the European Commission in its row with Warsaw over freedom of Poland's court system.
The previously reticent Merkel, speaking in Berlin, said she took the issue "very seriously" and would talk about it with Commission President Jean-Claude Junker on Wednesday.
In July, the commission, the European Union's executive, gave Warsaw a month to address its concerns about reforms it saw as interfering with an independent judiciary.
Warsaw's reply signaled that the ruling nationalist and euroskeptic Law and Justice (PiS) party had no intention of backing down and even doubted the commission's right to intervene.
While two of the new Polish laws questioned by the commission have been sent back for reworking by an unexpected presidential veto, a third one, giving the justice minister powers to fire judges, has become law.
The commission said it undermined the independence of the courts and therefore EU rules.
"This is a serious issue because the requirements for cooperation within the European Union are the principles of the rule of law. I take what the commission says on this very seriously," Merkel said at a news conference.
"We cannot simply hold our tongues and not say anything for the sake of peace and quiet," she said.
Polish Justice Minister Zbigniew Ziobro said Merkel's remarks showed the criticism was political, rather than factual.
"I'm convinced that Polish government will be executing its targets despite political emotions that appear in politicians' statements," Ziobro told reporters in Warsaw.
"Every country which is independent within the EU has its own laws and should settle its problems within democratic mechanisms," he said in remarks broadcast on state TV.
In its reply to the commission on Monday, the Polish foreign ministry said the legislative process of overhauling its judiciary was in line with European standards.
It called the commission's concerns groundless and noted that judiciary was the province of national governments, not the commission.
"We have received the reply from the Polish government. Regarding the point that we have no competence in this sphere, this is something that we would actually quite powerfully refute," a commission spokeswoman said.
"The rule of law framework sets out how the commission should react should clear indications of a threat to the rule of law emerge in a member state. The commission believes that there is such a threat to the rule of law in Poland," she said.
The commission said in July that it would launch legal action against Poland over the judicial reforms. It also said that if the government started firing Supreme Court judges, the commission would move to suspend Poland's voting rights in the EU — an unprecedented punishment that would, however, require the unlikely unanimous support of all other EU governments.
Merkel's remarks on Tuesday followed openly critical statements from French President Emmanuel Macron, who said last Friday that Poland was isolating itself within the EU and Polish citizens "deserved better" than a government at odds with the bloc's democratic values and economic reform plans.
In another unprecedented sign of defiance against the EU, the Polish government ignored an order by the EU's highest court to cease logging in the Bialowieza forest.
The court will convene September 11 to decide how to react to Warsaw's failure to honor the injunction, the first in EU history.
As the EU's spats with the PiS government get increasingly tense, the bloc's member states are due to discuss again this autumn whether the situation in their largest ex-communist peer merits launching an unprecedented Article 7 punitive procedure.
The maximum punishment under the procedure, however unlikely, would be stripping Poland of its voting rights in the EU over not respecting democratic principles on which the bloc is built.