* Polish judges say top court reform is illegal
* Government says court verdict is non-binding
* EU, US concerned over rule of law in Poland
By Wiktor Szary
WARSAW, March 9 (Reuters) - Poland's top court ruled on Wednesday that the government's planned overhaul of the tribunal was illegal, deepening a constitutional crisis that has stirred concerns about democracy and the rule of law in the EU's largest eastern member.
The ruling right-wing Law and Justice party (PiS) has approved a law increasing the number of judges needed to make rulings and changing the order in which cases are heard. It also rejected court appointments made by the previous government.
The government's critics say the changes undermine the court's effectiveness, while the European Union and the United States have also expressed concerns.
PiS says the changes are needed to reflect the new balance of power in Poland after its landslide election win last year.
"Dramatically limiting the court's ability to function independently and thoroughly contravenes Poland's (political) system and cannot be tolerated," Judge Stanislaw Biernat said, announcing the ruling at the end of a two-day court sitting.
The government said it regards the ruling as non-binding.
The timing of the court's verdict is politically sensitive.
The Council of Europe, a human rights body, is due to issue an opinion this week on Poland's legal changes.
The European Commission, the EU executive, has said it wants to see that opinion before making its own assessment of Poland's adherence to EU standards on the rule of law.
Critics say the changes, which prompted Brussels to launch the rule of law procedure for the first time in its history, have paralysed the court's work, making it difficult for judges to review, let alone challenge the government's legislation.
The government said before Wednesday's ruling that it would not publish the court's verdict in the official journal - a legal requirement - arguing that the tribunal's proceedings were unlawful as they did not follow rules outlined in the new law.
A leaked draft of the Council of Europe's opinion on the changes said the reform of Poland's top court threatened the rule of law.
PiS leader Jaroslaw Kaczynski said the draft was "legally absurd," signalling the government was unlikely to back down in the dispute. (Reporting by Wiktor Szary; Editing by Gareth Jones)