The arrested protesters were among hundreds who entered the restricted compound of Government House in Bangkok after joining a rally at a park led by Sondhi Limthongkul, a media tycoon.
Thaksin Shinawatra, the prime minister, said during his weekly radio programme that the protesters illegally encroached on government property.
Sondhi, Thaksin's former business associate, has been criticising the prime minister for several months by hosting weekly anti-government roadshows around the country.
He and other critics accuse Thaksin of abusing his power, cronyism, corruption, and other acts undermining King Bhumibol Adulyadej - serious allegations in a country where the king is widely revered.
Thaksin said on radio the rally had been instigated by those who turned against him after they failed to gain business favours from his government. He did not elaborate.
"We have to enforce the law. I have been quite patient but they went to the extent of breaking down the gate of the Government House in disregard of a major public property. This is unacceptable"
Thaksin Shinawatra, Thai prime minister
"We have to enforce the law. I have been quite patient but they went to the extent of breaking down the gate of the Government House in disregard of a major public property. This is unacceptable. They did this around midnight," Thaksin said.
Surapong Suebvonglee, the government spokesman, said protesters broke open the gate's padlock and chain before moving into the compound.
But protesters told a radio station that they did not use violence and said police had opened the gate.
Witnesses said police broke up the rally after the protesters left the compound peacefully without damaging any property.