Queensland Premier Campbell Newman says Clive Palmer is accusing him of corruption because his government stood up to the billionaire's demands for preferential treatment.
Hours after being declared the new federal MP for the seat of Fairfax, Mr Palmer used his victory press conference to accuse Mr Newman's government of corruptly favouring some private firms over others and said he would prove it.
He also claimed Mr Newman and Attorney-General Jarrod Bleijie were trying to hold the justice system to ransom over new laws targeting bikies and sex offenders.
But the premier hit back, saying the Palmer United Party leader was now fair game for criticism as an MP.
"His claims are essentially due to the fact that this government stood up to his demands that we provide preferential treatment for his commercial mining interests in Queensland," Mr Newman said.
"He didn't like it but we will always stand up to somebody who does not want to use due process and follow the law."
He warned that Mr Palmer would have to declare his pecuniary interests once he was sworn in.
He also pledged to make sure the mining magnate fulfilled environmental and employment obligations at his nickel plant in Townsville.
Mr Palmer said he had "direct evidence" the government had been benefiting certain private companies to the disadvantage of others.
"We'll be revealing that information soon so people can see that," he told reporters.
He also accused the premier and attorney-general of a "cowardly" attack on the judiciary.
"The government seems to want to be able to set the penalties for people. In Australia we enjoy democracy based on the separation of powers," he said."What Campbell Newman wants to do is take the blindfold off Lady Justice and stand behind her with a knife in her back and say, `you do this or I'll knife you'."