'This is really weird' – Hillary Clinton reveals seminal 'back up you creep (Trump) moment' she’d do differently from 2016 election (watch the moment)

Hillary Clinton says she knew the risks, but not telling Donald Trump to "back up you creep" as he stalked her on the presidential debate stage sticks out as the seminal mistake of her 2016 campaign.

The former US Secretary of State brought up the notorious incident in Auckland last night when asked by former New Zealand Prime Minister, Jenny Shipley, what was the biggest mistake of her failed campaign.

"Trump was stalking me on the stage, and invading my personal space, leering at me, making faces at me," Clinton told a packed audience at Auckland's Spark Arena on Monday night.

"Now I did prepare for the debates, I also prepared to be President. I thought that's what you did in order to do the job.

"And in preparing for the debate I though it was very important for me to maintain my cool, not get thrown off balance, certainly not get angry, but in real time while he is stalking me I'm thinking, you know 'this is really weird' and maybe I should just turn around and tell him 'back up you creep'."

The incident Clinton is referring to occurred on October 9, 2016, in the second presidential debate in a St. Louis town hall.

Clinton outlined the thoughts that ran through her head during Trump's intimidation tactic, and the risks she was weighing up at the time in terms of the potential fallout.

"Now I have to say I didn't do it. But I've thought since then that we were in this reality TV campaign and he was our first reality TV candidate and viewers are voters," Clinton said.

"And so perhaps if I had been willing to risk that - it was a big risk because I could just see the headlines afterwards: 'She can't take it, she blows up, she attacks Trump'.

"So I knew that's what he was trying to get me to do, but I kept thinking maybe I should do that.

"But I didn't and I've thought a lot about that, because if we're going to have these high stakes elections be more like entertainment then people who run for office are going to have to have more skills to deal with it, and I think that was one of the missed opportunities."

Ms Clinton spoke for around an hour Monday night before a packed audience at Auckland's Spark Arena.