Measures placed on Poland's judicial system by the EU have been rejected as unconstitutional by Warsaw's top court.

Judge Stanislaw Piotrowicz of Poland's Constitutional Tribunal said the order to disband a panel created to oversee high court judges was "not in line" with the Polish constitution.

The European Court of Justice (ECJ) told the Warsaw government led by Prime Minister Mateusz Morawiecki to suspend the procedural panel, which the EU said "infringes upon the independence of the judiciary in Poland and is incompatible with the primacy of the law of the Union."

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The decision sets Warsaw on a collision course with Brussels and the European Commission, not for the first time. The row over the impartiality of Poland's judges has been boiling for some years now. 

Even former judges of the country's constitutional court argued that disagreeing with the ECJ would increase the likelihood of Poland being forced out of the bloc. 

A ruling against the ECJ "would be a drastic violation of the obligations of a member state and a further step towards taking the country out of the union," a group of former judges warned. 

Along with the introduction of the disciplinary panel, which according to the ECJ impairs the judiciary's non-political stance, the new rules prevent judges from referring cases to the European Courts. 

The disciplinary chamber has the power to expose judges to criminal proceedings or cut their salaries, something the Polish government led by the Law and Justice party argues is necessary to tackle corruption.