BUDAPEST/ROTTERSDORF, Germany (Reuters) - The leader of the main center-right party in the European parliament said on Tuesday that Hungarian Prime Minister Viktor Orban must apologize for his criticism of the EU or his ruling Fidesz party could be suspended from the grouping.

FILE PHOTO: Hungarian Prime Minister Viktor Orban delivers his annual state of the nation speech in Budapest, Hungary, February 10, 2019. REUTERS/Bernadett Szabo/File Photo

Orban, an outspoken nationalist, wants to remain in the EPP, Fidesz said on Tuesday, despite growing pressure within the European Parliament’s biggest grouping to suspend or expel it.

The Hungarian leader has long been at loggerheads with Brussels over his hardline stance on immigration and accusations - which he denies - that he is undermining the rule of law. The feud is escalating ahead of European Parliament elections in May.

“Viktor Orban must immediately and permanently end his government’s anti-Brussels campaigns,” Manfred Weber, a German conservative and the center-right European People’s Party (EPP) candidate to be EU Commission President, told Bild newspaper.

Speaking to journalists in the German town of Rottersdorf Weber said that in recent weeks “Viktor Orban and the Fidesz have crossed again red lines” and added that all options were on the table, “especially the option of expulsion and going away, going our future way without Fidesz”.

Orban’s party said in an emailed statement, “Fidesz does not want to leave the (European) People’s Party, our goal is for anti-immigration forces to gain strength within the EPP”.

The EPP will vote on March 20 on whether suspend or exclude Fidesz. To pass, it requires a simple majority of those of the EPP’s 260 delegates who will be present.

Jean-Claude Juncker, the outgoing head of the European Commission, said on Tuesday he thought Fidesz no longer had a place in the EPP.

Orban has launched a media and billboard campaign that frames the May elections as a choice between forces backing and opposing mass immigration and that vilifies Juncker.

However, on Tuesday the Hungarian leader said he welcomed an initiative by French President Emmanuel Macron for reforming the EU.

“In the details, of course, we have differences of views, but far more important than these differing opinions is that this initiative be a good start to a serious and constructive dialogue on the future of Europe,” he said in a statement to Reuters.

Weber told Bild newspaper he expected an apology to EPP member parties, an immediate and permanent end to Orban’s anti-EU campaigns, and renewed government support for the Central European University (CEU) to stay in Budapest.

CEU was forced out of Hungary and plans to relocate to Vienna from September as Orban wages a bitter campaign against its founder, U.S. billionaire George Soros, accusing him of supporting immigration to undermine Europe’s way of life. Hungarian-born Soros, 87, denies that.

The EPP has 217 lawmakers in the 750-strong EU legislature, 12 of them from Fidesz. It is expected to remain the biggest parliamentary group in the May elections, although likely weakened, opinion polls show.

Far-right, populist parties are expected to perform well.