The Council of Europe says reforms to Poland's constitutional court "would undermine democracy" in the country.
The council's Venice Commission, an advisory body on constitutional matters, said on March 11 that the reforms put forward by the Polish government would also weaken "human rights and the state of law."
In December, Poland's president signed into law an amendment to how its constitutional court makes rulings, which critics say will unfairly strengthen the government's influence within the court.
The amendment, signed into law by President Andrzej Duda on December 28, requires the 15-member court to adopt most of its rulings by a two-thirds margin and with at least 13 judges present for the most contentious cases.
Critics say that will force the constitutional court to include five judges recently appointed to the body by the ruling party-dominated parliament in all key decisions in order to achieve a quorum.
The Strasbourg-based Council of Europe is a regional intergovernmental organization of 47 member states that aims to promote human rights, democracy, and the rule of law.
Based on reporting by AP and AFP