Former Prime Minister Sir John Key may have left Parliament, but he still can't escape that infamous ponytail-pulling scandal.

Key was forced to revisit the embarrassing incident in an interview with Australian broadcaster ABC.

"What happened was, there was a local café I went to, there was a bit of tom-foolery with the waitress, it was all very good-hearted, but in hindsight one of them wasn't a big supporter of mine and went to the media," Key told the station.

Asked what he did, he said: "I tugged it."

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"And you're Prime Minister of the country?", the ABC interviewer Tom Switzer asked. "That's very unorthodox."

"As I say, I did some very dumb things," Key said.

At the time, Key apologised to the waitress, Amanda Bailey, for pulling her hair over several months when he visited his local café Rosie's near his Parnell home.

Key joked that he actually "became more popular" after the incident.

"People could see ... obviously it was a misjudgment of the situation but not meant to be in any way kind of the way some people want to portray it.

"It was meant to be light-hearted, it was a bit of a joke, and it was a bit of a joke initially, but there's no question that it went [a bit] far."