Yuriy Haisinskiy said his move came after Minister Yuriy Lutsenko had accused his colleague in the Kiev region, Alexander Kuzovkin, and himself of blackmailing President Viktor Yushchenko over his son's behavior.
"I have never blackmailed anyone, and I have never threatened anybody," Haisinskiy said.
In late May, Kuzovkin was beaten up in the Ukrainian capital. Some media reports suggested Yushchenko's 19-year-old son, Andrei, had been involved. He has already caused something of a public stir by reportedly violating traffic regulations in the capital and driving an ostentatiously expensive BMW in a country where average wages are under $100.
The Interior Ministry is investigating the attack, and Lutsenko has told reporters that Kuzovkin had allegedly been drunk and tried to blackmail the president and the public.