The president of the European Commission Ursula von der Leyen stood by her vice-president Vera Jourova Tuesday, after Hungary's hardline prime minister Viktor Orban demanded her resignation.
Jourova, the commissioner charged with defending EU values and transparency, had branded Orban's Hungary an "ill democracy" in a news magazine interview.
She is due to present a report on the state of the rule of law in all EU member states Wednesday, in which Orban's government is expected to face strong criticism.
On Tuesday, Orban sent von der Leyen a letter accusing Jourova of humiliating the Hungarian people. Hungary also cut off political contacts with the Czech commissioner.
EU Commission spokeswoman Dana Spinant confirmed von der Leyen had received Orban's letter and would reply.
But she added: "Our concerns when it comes to the rule of law situation in Hungary are well known.
"President von der Leyen works closely with Vice President Jourova on the rule of law. And the vice president has the President's full trust," she added.
Jourova also received support from Germany, which holds the rotating EU presidency.
In a tweet, Germany's European affairs minister Michael Roth told Jourova "the European Union needs your impartial and clear mind!
"All member states need to be treated equally and abide by the same rules, enshrined in our treaties," he added.
- "Her resignation is indispensable' -
Orban is due in Brussels Thursday for a summit of the 27 EU leaders, and negotiations surrounding the EU budget had been hampered by the rule of law dispute.
European lawmakers and several member states want to tie EU funding for countries like Hungary to their respect for democratic legal values.
But Hungary and Poland, accused of a slide into populist authoritarianism, fiercely oppose this and have threatened to veto Europe's recovery plan.
Germany's Angela Merkel has been working to negotiate a compromise arrangement to protect EU funds from being misspent.
But Hungary's Justice Minister Judit Varga rejected the proposal as unacceptable.
Ambassadors from EU member states will meet on Wednesday ahead of the summit to discuss this.
The EU has a so-called "Article 7" procedure probing whether Hungary is undermining European legal standards and democratic values.
The row with Jourova will further embitter this fight.
Orban wrote: "The statements of Vice President Vera Jourova are incompatible with her current mandate, therefore her resignation is indispensable."
Orban was reacting to Jourova's description of Hungary in an interview with German news magazine Der Spiegel last week.
"Mr Orban likes to say he is building an 'illiberal democracy'," Jourova told Der Spiegel, "I would say: He is building an ill democracy."
Hungarian Foreign Minister Peter Szijjarto said Monday he expected the rule of law report to be little more than a "political statement".
- 'No one above criticism' -
Jourova herself, in comments to AFP Tuesday, rejected any suggestion that she had offended the Hungarian people.
"I have nothing but huge respect for the Hungarian people and the choices they make.
"But this does not mean we should not speak, also critically if needed, about actions of governments and elected representatives…," she added.
"In democracy, no one's actions are above criticism."
Budapest and its ally in Warsaw have long been at loggerheads with Brussels over democracy issues and immigration.
Orban has been accused of undermining democratic values by, among other issues, persecuting opposition media and forcing the closure of foreign-owned universities.
Pro-government Hungarian media often attack EU commissioners, accusing them of being puppets of US financier and philanthropist George Soros.
On Monday, Hungary and Poland set up a think tank to counter the "mainstream liberal" and the "pro-migration" ideas they say dominate in Brussels.