"This is just a scrap of paper," Orban said yesterday in an interview with state radio, referring to a document published by the government on Thursday said to come from the US embassy in Budapest.
"We were given a paper that is a loose collection of accusations that we have heard from opposition parties over the last four years. If it weren't in English, I would think it was written by opposition parties."
State Department spokeswoman Jen Psaki yesterday refused to go into any detail or "comment on private diplomatic communication".
"We, of course, have a dialogue with the Hungarian government at many levels on a wide range of issues, including the fight against corruption," she told reporters in Washington.
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Orban also told an audience of US and international business people in the Hungarian parliament that the US and Hungary remained "good partners".
"Between us there is deep political association, economic partnership, and mutual respect for our cultures," Orban told the local branch of the American Chamber of Commerce, which was celebrating its 25th birthday in Hungary.
Psaki did confirm however that the head of the tax office, Ildiko Vida, was among them.
Vida revealed earlier this month that she was one of the six, and rejected the "wicked" accusations. Last Sunday, several thousand demonstrators called for her resignation.
The row has further soured relations between Washington and Hungary, a NATO and EU member, which have worsened since the right-wing Orban took power in 2010.
In September, US President Barack Obama criticised Hungary for harassing civil organisations, while the top US diplomat in Hungary, Andre Goodfriend, said last month that "negative trends" have "rapidly taken hold".