Hanson-Young stumbles on Greens' super

Greens Senator Sarah Hanson-Young has joined deputy Liberal leader Julie Bishop in stumbling over superannuation policies.

Senator Hanson-Young told ABC radio on Wednesday that the minor party would seek to tax superannuation at the same rate as income.

"In order to make it fair, you should be paying the same tax rate as you do for what you're earning on your super. Why not? Why shouldn't it be the same?" she said.

Labor MP Mark Butler, who was appearing on the same program, labelled Senator Hanson-Young's comments "extraordinary".

"I'm not quite sure that Sarah has quite outlined the Greens' party approach to superannuation because it would essentially undo 30 years of retirement incomes policy," he said.

Senator Hanson-Young later corrected her comment.

"I've had a text from my chief of staff sitting outside, sending me the table," she said.

"It's basically, as I was saying, a progressive tax rate."

Ms Bishop had a self-confessed "gotcha moment" on Melbourne radio on Tuesday when she was unable to say how the coalition's super transition-to-retirement changes worked.