The EU has given Poland one month to allay its concerns over judicial reform plans.
The prospect of Polish politicians firing and replacing judges prompted the ultimatum on Wednesday.
Warsaw risks an Article 7 procedure to punish a member state for not respecting common laws and values.
European Commission Vice President Frans Timmermans told reporters in Brussels:
“The Commission recommends the Polish autorities to solve all the problems identified within one month.
“The Commission’s recommendation asks the Polish authorities not to take any measure to dismiss or force the retirement of Supreme Court judges. If such a measure is taken, the Commission is ready to immediately trigger the Article 7 (1) procedure.”
Poland’s ruling right-wing Law and Justice Party is determined to press ahead with its reforms.
But the European Commission is concerned at a law giving the justice minister the power to appoint and dismiss the heads of lower courts.
Brussels says the measure undermines judicial independence and therefore breaks EU treaty rules.
The most controversial part of the Polish government’s plans, covering Supreme Court nominations, was vetoed by Poland’s President Andrzej Duda after mass street protests.
Reacting to the ultimatum, Poland’s deputy foreign minister in charge of European affairs, Konrad Szymanski, told the PAP news agency that Brussels’ objections were unjustified.
“The European Commission should take into a greater account in its reflections the fact that the organisation of the justice system belongs to the jurisdiction of the member states, which, in their political and legislative process make their own decisions,” Szymanski said.
Rafal Bochenek, a government spokesman, said that Poland would not agree to interference by the EU.
“We will not tolerate any blackmail from EU officials, especially blackmails that are not based on facts,” Bochenek told PAP.
“We regret that Mr. Timmermans, without knowledge of the draft bills and Polish law, comes up with a hurtful criticism of Poland.”