Prime Minister Viktor Orban's chief of staff on Thursday rejected criticism of the Hungarian government by the U.S. ambassador to Budapest, saying her remarks amounted to interference in Hungary's affairs.

"For me as a voter it is downright irritating that a diplomat should come here and tell us how to live or how our voters should live," said Janos Lazar, one of Orban's top lieutenants.

Since assuming power in 2010, Orban's government has come under fire from the European Union and the United States for curbing media freedoms, its reforms of the court system, centralisation of power and a crackdown on NGOs.

U.S. ambassador Colleen Bell said on Wednesday that corruption in Hungary was still a serious concern, using the secrecy surrounding Hungary's deal with Russia over its nuclear plant in Paks as an example.

"Increasing centralisation of power creates conditions that mean that many of the big decisions that will impact Hungary for generations to come remain opaque," Bell said.

"We urge an immediate end to heavy-handed tactics against civil society organizations."

The ambassador also criticised Hungary's attitude towards refugees amidst the migration crisis in Europe.

"We can relegate nationalist, intolerant rhetoric to the dust heap where it belongs," Bell said.

Lazar was asked at a routine news conference about Bell's remarks.

"As a country we are not subjugated to the United States of America, and we do not want to be either," he said. "Diplomats delegated here ought to get used to this after five years (of the Fidesz party in power)."

"It is not us that need a reality check, but the Embassy of the United States of America, in view of how they interfere in Hungary's domestic politics, what hasty and simplistic judgements they pass on a society," Lazar added.