The resolution urged the Polish government to respect rulings by the country's Constitutional Tribunal. In total, 513 MEPs from five of the eight groupings in the European Parliament voted for the motion, while 142 voted against.
Poland is locked in a constitutional crisis after the conservative Law and Justice (PiS) party introduced sweeping reforms to legal and other institutions after coming to power in October.
The Constitutional Tribunal has rejected PiS-backed changes to the way it functions. PiS, in turn, has refused to recognise that ruling, claiming it is invalid.
Wednesday's resolution was drawn up by the largest group in the European Parliament – the European People's Party (EPP) – together with Socialists, and backed by several other groupings.
Ryszard Legutko, an MEP from Law and Justice, called the resolution “absurd, damaging, non-credible and counter-productive.”
Grzegorz Schetyna, head of Poland’s opposition Civic Platform (PO) party, said earlier: “This is an important day because it shows that violating the constitution and the law in Poland cannot take place without a response from the EU.”
He added that under PiS, Poland was “on a straight path to leaving the EU.”
But Senate Speaker Stanisław Karczewski, of Law and Justice, said the European Parliament resolution was a result of the Polish opposition “informing on Poland” to European institutions.
The Constitutional Tribunal on 9 March rejected a series of controversial changes to the way it functions introduced by PiS. The court said the changes, pushed through at the end of last year, prevented the tribunal from working “reliably and efficiently.”
Under a bill put forward by PiS, the Constitutional Tribunal was required to pass rulings with a two-thirds majority, rather than the previous simple majority. Thirteen out of all 15 judges had to be in attendance, rather than nine judges, as previously.
Critics said the PiS-backed changes were designed to paralyse the tribunal.
PiS argued it was unfair that a tribunal with a majority of judges appointed under the previous parliament should be able to scupper flagship policies for which the party secured a mandate in democratic elections.
In January, the European Commission said it was starting a probe into whether controversial laws pushed through by Law and Justice violate EU standards.