Spain’s Prime Minister Pedro Sánchez has warned that the top court’s decision to block a parliamentary initiative has unleashed an institutional crisis that is without precedent in the country’s modern era and among European democracies.

The Socialist prime minister was speaking the day after the Constitutional Court had accepted an appeal by opposition conservatives against a government amendment of the judiciary, thus halting the legislation’s passage through parliament.

Last week, Congress approved the change, which reduces the parliamentary majority needed to appoint senior judges. However, the court ruling prevents the legislation from proceeding to the Senate, where it was due to be voted on later this week.

In a televised statement, Sánchez said he accepted the court ruling but it meant that “for the first time, our legitimate representatives, democratically elected by Spaniards … are being prevented from carrying out their representative duty.”

He added that this situation “has no precedent in the democratic history of our country, nor in Europe’s institutional spaces.”

The prime minister blamed the clash on the conservative Popular Party (PP), which presented the appeal against the amendment, having claimed it violated constitutional norms after being included at the last minute as part of the government’s reform of the penal code.

Sánchez accused the PP of trying to use the judiciary to wield political power that it had lost in elections.

Sánchez’s Socialist Workers’ Party (PSOE) and its junior coalition partner, Unidas Podemos (UP), had called for two of the Constitutional Court’s judges to be recused, arguing that their tenures had expired and so they were effectively ruling on their own future. However, that claim was rejected.

The court’s decision now means that a four-year impasse caused by a disagreement between the PSOE and the PP over the appointment of new judges is set to continue. Sánchez said his government will continue to seek a solution to the standoff.

PP leader Alberto Núñez Feijóo welcomed the ruling and said that the government had violated constitutional rules with its attempt to reform the judiciary, claiming that Sánchez had drifted toward “extremist populism.”

“This is an outlandish legislature that undermines the democratic tradition of our country,” he said. “The government is obsessed with controlling our state institutions.”

The court ruling does not affect other changes that Congress approved as part of the penal code reform. They include the elimination of the crime of sedition and reductions of sanctions for misuse of public funds in certain cases. The opposition has accused the government of pandering to Catalan nationalists with both changes.