Greek Prime Minister Kyriakos Mitsotakis called for Viktor Orbán's Fidesz party to be expelled from the EPP | John MacDougall/AFP via Getty Images Leaders urge Europe’s center-right alliance to expel Orbán Mitsotakis and 12 other national chiefs leaders say Hungarian PM’s rule by decree means he should be kicked out of European People’s Party.

Prominent national leaders in the European People's Party (EPP), including Greek Prime Minister Kyriakos Mitsotakis and his Norwegian counterpart Erna Solberg, called Thursday for Hungarian Prime Minister Viktor Orbán's Fidesz party to be expelled from the Continent's center-right political grouping.

The leaders made their call in a letter, after the Hungarian parliament this week approved a measure to let Orbán's government rule by decree without any specified end date, due to the coronavirus crisis.

Their move triggers a formal process that could result in Orbán's party being kicked out of the EPP, the EU's predominant political force.

In their letter to former European Council president Donald Tusk, the leaders of 13 national member parties including Mitsotakis, Solberg, Petteri Orpo from Finland's National Coalition Party and Rutger Ploum from the Dutch Christian Democratic Appeal, said the Hungarian move is "a clear violation of the founding principles of liberal democracy and European values."

"We wish to express our full support to President Donald Tusk and the entire EPP leadership in upholding the integrity of our political family," the letter said. "We call on the expulsion of Fidesz from the EPP in accordance with article 9 of the EPP statutes."

"We fear that Prime Minister Orbán will use his newly achieved powers to further extend the government's grip on civil society," it added.

The letter, initiated by Sweden's Moderate Party, was not signed by leaders of some of the EPP's biggest national parties, such as Germany's ruling Christian Democrats (CDU), France's Les Républicains or Spain's Popular Party. But it contains enough signatures to bring the issue to a vote at the EPP's next political assembly.

The next meeting of the assembly is scheduled for June but EPP officials said the letter may bring matters to a head more quickly.

Under EPP rules, the EPP presidency "or seven Ordinary or Associated Member Parties from five different countries" can submit a proposal for the suspension or exclusion of a member party.

The EPP suspended Fidesz last March over concerns about the rule of law in Hungary and anti-Brussels rhetoric. But the national parties that make up the alliance have since been unable to agree on whether to let Fidesz back into the fold or push it out completely. Meanwhile, Fidesz MEPs have remained members of the EPP group in the European Parliament.

Swedish MEP Tomas Tobé, who was commissioned by his Moderate Party to write the letter, said it was now up to Tusk to "see which actions to take." Though German and French EPP parties are not signatories, Tobé noted several members of the CDU "have been critical" of Orbán lately.

"Let's see how the others react to the letter," Tobé said.

Lili Bayer contributed reporting.