Polish Prime Minister Mateusz Morawiecki has told fellow European Union leaders in a letter that the EU risks becoming a "centrally managed organism run by institutions deprived of democratic control".
Mr Morawiecki said this was "a dangerous phenomenon that threatens the future of our union".
Poland's populist right-wing government has been at odds with the EU for years over controversial judicial reforms.
A ruling by the Polish Constitutional Court this month questioning parts of EU law has raised tensions further.
In his letter, Mr Morawiecki added that Poland would remain a "loyal member" of the EU and appealed to the bloc's leaders to be "open to dialogue" on reforming the EU.
"I truly believe that together, in the spirit of mutual respect and understanding, without imposing one's will on others, we can find a solution that will strengthen our European Union," he said.
The letter comes ahead of a summit of EU leaders this week and in the wake of the ruling from Poland's Constitutional Court challenging the primacy of EU law.
The ruling was widely criticised by other EU members such as France and Germany. Analysts said it could be a first step towards Poland one day leaving the EU.
The court stated that parts of the EU treaties were "incompatible" with the Polish constitution and warned the EU's Court of Justice against interfering with Poland's judicial reforms.
The reforms are being pushed through by Poland's ruling Law and Justice (PiS) party and have long been a bone of contention between Warsaw and Brussels.
The EU says they undermine judicial independence and could roll back democratic reforms, while the Polish government says they are necessary to root out corruption in the judiciary.
Mr Morawiecki is due to address the European Parliament tomorrow.
In his letter, he said that the primacy of EU law was "not unlimited" and that "no sovereign state" could say otherwise.
"Today we are dealing with a very dangerous phenomenon whereby various European Union institutions usurp powers they do not have under the treaties and impose their will on member states.
"This is particularly evident today as financial tools are being used for such a purpose," he said -- a reference to new powers for the European Commission to withhold EU payouts if bloc norms on corruption and rule of law are seen as being threatened.
Mr Morawiecki warned that "centrally managed institutions, deprived of democratic