The European People's Party (EPP) suspended Hungary's ruling Fidesz party until further notice, and set up a panel led by former European Council president Herman Van Rompuy to supervise Fidesz's respect of the EPP's basic values, Trend reporting to Xinhua.
EPP President Joseph Daul announced the party's decision in a tweet on Wednesday.
The announcement followed a vote in the EPP assembly in Brussels by delegates from its member parties. The decision passed with 190 in favor and 3 against.
"The suspension entails: No attendance at any party meeting; No voting rights; No right to propose candidates for posts," Daul tweeted.
The main center-right grouping in the European Parliament has had trouble with Fidesz, a long-term EPP member. Several EPP member parties have criticized Fidesz for not complying with the group's values and rules.
A week earlier, senior EPP leader Manfred Weber visited Budapest and tried to solve the problems with Hungarian Prime Minister Viktor Orban. Weber wanted Orban and his Fidesz party to stop his government's anti-EU campaign, let the Central European University (CEU) founded by U.S.-Hungarian billionaire George Soros stay in Budapest, and apologize to other EPP member parties.
Weber said his talks with Orban had been constructive but "problems were not yet solved."
Alongside Van Rompuy, the other members of the evaluation commission are the Wolfgang Schussel of Austria and Hans-Gert Pottering of Germany.
A similar three-men commission had been set up by the EU back in 2000, when Austria's conservative governing party formed a coalition with the far-right.
Orban took part in the debate preceding the vote, and held an international press conference streamed live by the Hungarian media, in which he underlined that a "compromise had been reached."
"We have disputes with only those members of the EPP who wanted us to be expelled, not with the majority of the EPP," he said.
He said that Fidesz was also to set up its own three-member commission tasked with negotiating with the EPP's commission.
Asked about the deadline for the commission to present its evaluation, Orban said that it would certainly take longer than a few months, and its work would likely last until after the European Parliament elections at the end of May.
He also said that the question of whether the Fidesz delegates to be elected in May -- 13 or 14 according to polls -- will join the EPP was still "an open question."
"As long as Fidesz does not completely restore the EPP's trust, they cannot remain full-fledged members," German CDU leader Annegret Kramp-Karrenbauer said earlier.
The mainstream conservative EPP is the largest political family in the European Parliament.