PM John Key admits he needs to conduct himself more carefully in public following last week's revelations he repeatedly tugged a waitress's ponytail in an Auckland cafe.

Prime Minister John Key says he sees himself as the most casual leader the country has ever had.

His comments come after a statement by waitress Amanda Bailey that Key had made her feel uncomfortable by repeatedly pulling her ponytail while she worked.

The hair-pulling is alleged to have happened numerous times over many months.

READ MORE: PM pulled waitress' ponytail

In an interview with TVNZ's Q and A programme broadcast on Sunday morning, Key said he had been trying a bit too hard to have fun.

"I shouldn't have done the things I've done. Obviously I regret that and I regret any harm that that has caused the young lady in question."

Key said he needed to make sure he was a bit more careful in the future, but he rejected people seeing what happened as a power imbalance in his favour.

He said he couldn't reverse what happened but he could learn from it.

"I'm a friendly guy that likes to interact with the public. I do like to have a bit of a laugh and I'm probably the most casual Prime Minister New Zealand has had."

Key said his casual approach had both advantages and disadvantages.