The European Union called on Poland's ruling conservatives to uphold the rule of law, and to refrain from adopting a reform of the constitutional court that might threaten its independence, in a letter seen Wednesday by AFP.

"I would expect that this law is not finally adopted or at least not put into force until all questions regarding the impact of this law on the independence and the functioning of the Constitutional tribunal have been fully and properly assessed," wrote the European Commission's vice president Frans Timmermans in a letter to Poland's foreign and justice ministers.