Respect LGBT rights or leave the European Union, Dutch Prime Minister Mark Rutte told Hungary's premier as EU leaders confronted Viktor Orban over a law that bans schools from using materials seen as promoting homosexuality.
Several EU summit participants spoke of the most intense personal clash among the bloc's leaders in years on Thursday night.
"It was really forceful, a deep feeling that this could not be. It was about our values; this is what we stand for," Rutte told reporters on Friday.
"I said 'Stop this, you must withdraw the law and, if you don't like that and really say that the European values are not your values, then you must think about whether to remain in the European Union'."
French President Emmanuel Macron called it a "cultural battle", acknowledging a deepening rift with increasingly assertive illiberal leaders that is hurting EU cohesion.
"To fight against homophobic laws is to defend individual freedoms and human dignity," he said, adding that Hungary should remain a member of the EU.
"Very Different Ideas"
Unless it rows back, Hungary faces a legal challenge at the EU's highest court. Luxembourg Prime Minister Xavier Bettel said Orban should also be subject to an as-yet untested procedure to cut EU funding for those who violate rules.
The new mechanism was introduced as closely aligned conservative governments in Poland and Hungary have shielded one another for years from sanctions under existing measures to protect EU democratic and human rights values.
The provisions for schools have been included in a law primarily aimed at protecting children from paedophiles, a link that Belgian Prime Minister Alexander De Croo described as "primitive".
Orban, who has been Hungary's prime minister since 2010 and faces an election next year, has become more conservative and combative in promoting what he says are traditional Catholic values under pressure from the liberal West.
Describing himself as a "freedom fighter", Orban told reporters before the meeting that the law was not an attack on gay people but aimed at guaranteeing parents' right to decide on their children's sexual education.
The EU is pushing Orban to repeal the law - the latest in a string of restrictive policies towards media, judges, academics and migrants.
Seventeen of the 27 EU leaders, including German Chancellor Angela Merkel, signed a joint letter reaffirming their commitment to protecting gay rights.
"We all made it very clear which fundamental values we adhere to," Merkel said.
She said she shared Macron's assessment that some EU countries have "very different ideas" about Europe.
Bettel, who is openly gay, said the only country other than Poland to support Orban in the discussion was Slovenia, whose prime minister has also been accused of undermining the independence of the media.
Bettel said it was time for Brussels to test its new procedure: "Most of the time, money is more convincing than talk."