BRUSSELS (Reuters) - The European Commission on Tuesday stepped up its latest legal case against Poland, where the ruling nationalists stand accused of bulldozing the independence of courts and judges, thereby undercutting democracy.

Governed by the Law and Justice (PiS) party, the EU’s largest ex-communist state has most recently enacted laws forcing into early retirement many Supreme Court judges. The bloc, rights groups and domestic political opposition decry that as going against the rule of law.

These moves came after the PiS had already exchanged many judges at the Polish Constitutional Tribunal and heads of many regular courts, while also tightening its grip on public media and controls over non-government groups since coming to power in late 2015.

Now, the head of the Polish Supreme Court has been defying the new law and the situation risks paralysing the court, which validates election results in the country of 38 million people.

“The Commission maintains that the Polish law is incompatible with EU law as it undermines the principle of judicial independence, including the irremovability of judges,” the EU’s executive on Tuesday as it took to a second level a formal infringement procedure against Warsaw.

Poland now has a month to make amends or the Commission will file a lawsuit at the bloc’s top European Court of Justice.

But the PiS remains defiant and enjoys broad public support - largely thanks to generous social spending - despite its many bitter feuds with the EU.