Julie Bishop has been caught out in a self-described “gotcha moment” when asked about the Coalition’s Transition To Retirement scheme on Tuesday morning.

The scheme allows workers to supplement their salary with superannuation before retirement, but changes announced in the May budget mean earnings on assets supporting workers’ transitions will be subject to the existing 15 per cent tax rate, from July 2017.

In an interview with 3AW‘s Neil Mitchell, the broadcaster quizzed Ms Bishop on the plan: “Are you aware of the transition to retirement scheme?”, he said.

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“I’m certainly aware that we have one, yes,” Ms Bishop responded.

Mitchell followed up: “How does it work?”

Ms Bishop: “Well, Neil, this is obviously a ‘gotcha’ moment. It’s not my portfolio.”

Mitchell responded: “This is the point. Neither you or Josh Frydenberg understand Transition To Retirement and this is where you’re hitting average people, not the fat cats, the average people.”

Ms Bishop: “I don’t accept that’s the case.”

It’s the second time a senior government minister has struggled with the Coalition’s Transition To Retirement scheme.

Mr Frydenberg had similar issues explaining the same policy earlier this month while being interviewed by Mitchell.

Ms Bishop also said she wouldn’t challenge prime minister Malcolm Turnbull for leadership, but when Mitchell asked if she would ever run for PM, she didn’t rule out the possibility.

“Never to run for the leadership? Well, I would never challenge Malcolm Turnbull for it if that’s what you mean. But of course I can’t say I would never do it if there was a circumstance, but I certainly don’t see one,” Ms Bishop said.

“But you’d never challenge?”, Mitchell asked.

Ms Bishop responded: “No. I don’t envisage that. I am very, very happy being the Foreign Minister. I have been deputy to a number of leaders and I think I play a positive role in that regard and most certainly my colleagues appreciate me being the deputy of the party.”