The European Commission decided on Tuesday to ask the EU's top court to suspend the functioning of the disciplinary chamber of Poland's Supreme Court in a major blow to the eurosceptic Polish government, which immediately questioned the move.

The European Union's executive arm said its move came after a preliminary ruling of the EU top court on November 19, which asked Poland's Supreme Court to rule if its new Disciplinary Chamber, appointed by the ruling PiS party, was independent.

The Polish Supreme Court ruled on December 5 it was not.

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"Despite the judgments, the Disciplinary Chamber continues to operate, creating a risk of irreparable damage for Polish judges and increasing the chilling effect on the Polish judiciary," said the Commission, the guardian of EU law, which trumps all national laws of EU countries.

"Today, the European Commission decided to ask the Court of Justice to impose interim measures on Poland, ordering it to suspend the functioning of the Disciplinary Chamber of the Supreme Court," the Commission said in a statement.

The Commission said its move was not linked to the new Polish draft law which has now cleared the lower chamber of Parliament in which PiS has a majority.

Poland's main judges' association says the draft law is intended to muzzle judges who question the legality of PiS changes to the judiciary.

"The Commission is closely monitoring developments," the EU executive arm said in the statement.

A Polish government spokesman said in response to the Commission action that the EU had no grounds to question Poland's judiciary reforms.

The EU and Poland's nationalist PiS government have been at odds over the rule of law since 2015 and the conflict shows no signs of abating since the PiS won a second term in office last October.

The head of the EU's top court, Koen Lenaerts, issued a veiled warning to Poland last week over its overhaul of the judiciary, saying there was no place in the EU for countries that do not have independent courts.