Malgorzata Gersdorf has branded the reforms, which lowers the retirement age of Supreme Court judges from 70 to 65, as a "purge" （Photo: AFP)

Poland's disputed top judge showed up at work on Wednesday in defiance of a retirement law pushed through by the right-wing government but criticised by the EU as a threat to judicial independence.

Chanting "Free courts!", "Constitution!" and "Irremovable!" several thousand supporters greeted Supreme Court chief justice Malgorzata Gersdorf as she made her way into the court building in central Warsaw.

Gersdorf has branded the reform -- which has put Poland's Law and Justice (PiS) government at loggerheads with Brussels -- a "purge".

Insisting that she has a six-year term under the constitution, Gersdorf, 65, refused to comply with the new rules that require her to step down immediately, cutting short her tenure that was set to end in 2020.

"I'm not engaging in politics; I'm doing this to defend the rule of law and to testify to the truth about the line between the constitution and the violation of the constitution," Gersdorf told journalists and supporters outside the court.

"I hope that legal order will return to Poland," she said.

Twenty-seven of the court's 73 judges are affected. Under the law, the judges can ask the president to prolong their terms, but he can accept or deny their requests without giving a reason.

Sixteen judges have made requests, according to Polish media reports.

'Rape of the Supreme Court' 

The European Union on Monday launched legal action against Poland over the new rules, which lower the retirement age of Supreme Court judges from 70 to 65.

It was the latest salvo in a bitter battle over sweeping judicial changes introduced by the PiS government that could end up in the European Court of Justice (ECJ), the bloc's top tribunal.

"Rape of the Supreme Court," thundered an editorial in leading liberal daily Gazeta Wyborcza.

Presidential aide Pawel Mucha insisted that Gersdorf was "going into retirement in accordance with the law" and said the court was now headed by Judge Jozef Iwulski, who was chosen by President Andrzej Duda as an interim chief justice.

The PiS government has refused to back down despite the EU legal action, insisting the reforms are needed to tackle corruption and overhaul a judicial system still haunted by the communist era.

"Every EU country has the right to develop its judicial system according to its own traditions," Prime Minister Mateusz Morawiecki told a session of the European Parliament.

Critics have warned that the judicial overhaul poses a threat to key pillars of democracy in the EU member state.

'Harassment' 

Amnesty International charged in a report last month that "judges are indeed experiencing political pressure in Poland" and said those who refuse to bow to the reforms have reported harassment including disciplinary proceedings.

"I would like my country to be free, democratic and to respect the separation of powers," Warsaw resident Grazyna Kwadrans told AFP at Wednesday's protest.

Anti-communist hero Lech Walesa will join demonstrations later Wednesday to support Gersdorf and other affected judges, his spokesman told AFP.

Gersdorf was long a member of the Solidarity trade union that was key to the toppling of communism in Poland in 1989.

She said after showing up for work that she plans to go on holiday from next week, and that Iwulski would be standing in for her during her absence.

"I'm not a replacement for, nor the successor of, the Supreme Court chief justice; I only fill in if she is absent," Iwulski said, appearing to contradict the presidential aide.

The European Commission, the bloc's powerful executive arm, said Monday that the PiS reforms undermine "the irremovability of judges" and judicial independence, breaching the country's obligations under EU law.

Poland has a month to respond and the dispute could end up in the European Court of Justice (ECJ), the bloc's top tribunal.

Brussels in December triggered so-called Article Seven proceedings against Poland over "systemic threats" to the rule of law, which could eventually see Warsaw's EU voting rights suspended.

Tens of thousands of Poles have hit the streets since the PiS government came to power in 2015, protesting at its judicial reforms and attempts to tighten Poland's already strict abortion law, among other causes.