Independent MP Bob Katter says the cross bench will move immediately on a royal commission into banks following the resignation of Liberal MP John Alexander.

Mr Alexander resigned on Saturday after revealing he "most likely" holds UK citizenship, leaving the coalition clinging to 73 seats in the 150 seat House of Representatives, not counting the Speaker.

Mr Katter on Sunday said the crossbenchers now hold the balance of power and would move immediately on the royal commission and on the issue of ethanol in the new year.

"For technical reasons it will be the second week of parliament, in my opinion, that we will be moving," Mr Katter said.

"If the government tries to play any silly game and circumvent the will of the people, the majority of that parliament, then they are walking on extremely dangerous ground.

"I would refer them to (Kings) James I and Charles I - they both lost their heads."

Mr Katter said if Prime Minister Malcolm Turnbull tried to stop a royal commission by calling a federal election "then God help him at the polls".

"Let him proceed at his peril," he said.