Poland has accused the European Commission of launching a politically motivated attack to strip the country of its voting rights in Brussels.

“Within a period of two years a significant number of laws have been adopted – 13 in total – which put in serious risk the independence of the judiciary and the separation of powers,” the vice-president of the commission, Frans Timmermans, told reporters in Brussels. “Judicial reforms in Poland mean that the country’s judiciary is now under the political control of the ruling majority. In the absence of judicial independence, serious questions are raised about the effective application of EU law.”

Timmermans added: “We are doing this for Poland, for Polish citizens.”

As reported by The Guardian, the Commission on December 20 advised European Union member states that the legislative programme of Poland’s government was putting at risk fundamental values expected of a democratic state by allowing political interference in its courts.

Poland’s Prime Minister Mateusz Morawiecki responded on Twitter: “Poland is as devoted to the rule of law as the rest of the EU.”

The Polish foreign ministry said in a statement: “Poland deplores the European commission’s launch of the procedure […] which is essentially political, not legal.”

A few hours later, Polish President Andrzej Duda gave a televised address to announce he had signed into law the two bills overhauling the judiciary.

According to The Guardian, the row represents the greatest crisis in the EU since Britain’s decision to leave the EU last year, with the Polish government showing little inclination to back down.

“It is with a heavy heart that we have decided to initiate Article 7.1,” Timmermans said. “But the facts leave us with no choice.”

At least 22 of the 28 member states will now need to vote in favour of the commission’s proposal for a formal warning, but Brussels is confident it has the numbers it needs.

Hungary also responded. Zsolt Semjén, Hungary’s deputy prime minister, immediately described the move as “unprecedented and astounding” and reiterated the declared intention of the prime minister, Viktor Orbán, to block any sanctions.

“The decision seriously damages Poland’s sovereignty,” Semjén said. “It is unacceptable that Brussels is putting pressure on sovereign member states and arbitrarily punishing democratically elected governments.”

According to The Guardian, the development will prove highly awkward for British PM Theresa May, who will be in Warsaw for a UK-Poland summit on December 21, at which she hopes to push forward her vision of a post-Brexit trading relationship with the rest of Europe.

The UK government has been ambiguous over its position, due to concerns that Brussels should not be meddling in domestic affairs.

Meanwhile, the European council president, Donald Tusk, a former Polish prime minister, and a party political rival to the Law and Justice party, urged Warsaw to “come to its senses”.

“I sincerely hope that the Polish government will … not seek a conflict at all cost in a case where it is simply not right,” Tusk said in Krakow, southern Poland.