Mr Kaczynski told Polish daily newspaper Gazeta Polska Codziennie the “program of deep changes in our country will not slow down, on the contrary”.
He said: “There cannot be any talk about reaching an agreement with powers that for years treated Poland as their own private loot.”
He added: “There is of course no way Poland would hand in a decision on the court reforms to the European Court of Justice. This is our internal competence guaranteed by EU law.”
PiS is accused of going against the rule of law by interfering in the judiciary in a series of reforms critics claim will limit judges’ independence.
Poland has now also been threatened with losing part of its EU funding if prime minister Mateusz Morawiecki does not walk back the reforms, which are a crucial part of his conservative platform.
However the defiant display by Mr Kaczynski is the latest in a string of indications Poland will stand firm against its critics and press ahead with the changes.
Today Poland received backing from three other European nations as the leaders of the Visegrad group released a statement telling the Commission to wind its neck in on interfering with the judicial reforms.
In a joint statement, the leaders of Hungary, Czech and Slovakia, alongside Poland, said: “EU institutions should treat all member states equally and act strictly within the remits of their respective Treaty-based competences.
“The right of member states to carry out domestic reforms within their competences should be respected.”
Mr Morawiecki, for his part, says the dispute between Poland and the EU is just a “misunderstanding” and has called for further dialogue between the two parties.
He and other central and eastern European leaders have demanded a greater role in the bloc and say they want to be taken more seriously by the Eurocrats at the centre of the EU.