European Commission chief Jean-Claude Juncker hit out on Thursday at Hungarian Prime Minister Viktor Orban over an anti-EU questionnaire campaign launched by Budapest.
The Hungarian government is posting questionnaires titled "Let's stop Brussels!" to households nationwide asking them how to deal with EU policies that it says threaten their independence.
"Having read this biased questionnaire, I would like to better understand Mr Orban's intentions," Juncker told reporters in Brussels.
"This way of talking badly about Brussels after having signed the Declaration of Rome says more about the author of the questionnaire than about the state of the European Union," Juncker added.
Juncker was referring to an event last month when Orban joined other EU leaders and signed a special declaration to mark the 60th anniversary of the EU's founding Treaty of Rome.
Orban's right-wing government has long been at odds with Brussels, particularly over an EU scheme that makes all member states take in migrants to ease the burden on frontline Mediterranean countries Italy and Greece.
Juncker called Orban a "dictator" at an EU summit in 2015 -- a remark Orban's spokesman later said was part of banter between the two men.
The Hungarian government questionnaire, announced by the government on Saturday, has six questions mostly asking citizens "what Hungary should do" about EU policies on immigration and economic issues like tax-raising powers.
One question asks "what Hungary should do" as "despite a series of recent terror attacks in Europe... Brussels wants to force Hungary to let in illegal immigrants".
Juncker meanwhile also criticised Hungarian lawmakers for approving legislation that could force the closure of a prestigious Budapest university founded by US billionaire investor George Soros.
"I don't like this decision," Juncker said, adding that EU commissioners would discuss the issue next week.
The English-language Central European university, set up in 1991 after the fall of Communism, has long been seen as a hostile bastion of liberalism by Orban's government.