Key, 53, stands accused by the waitress of yanking her ponytail over a six-month period when he visited her Auckland café with his wife, Bronagh. In an anonymous post at the Daily Blog site she said the prime minister had acted “like the schoolyard bully tugging on the little girls’ hair trying to get a reaction.”

The premier apologised via a spokesperson, who insisted Mr and Mrs Key had a good relationship with staff at the café. “His actions were intended to be light-hearted,” said the spokesperson. “It was never his intention to make her feel uncomfortable and he has apologised to her.”

In her blog the waitress said Key had continued to pull her ponytail despite her attempts to avoid his attention. “He would come up behind me when I was at the ordering terminal, tug on my hair and then pretend that his wife, Bronagh, had done it (much to her embarrassment), and she would tell him to stop it. As he rounded the corner behind me he commented ‘that’s a very tantalising ponytail’,” she wrote.

The anonymous blogger said that despite her objections Key subsequently grabbed her hair again, having approached making “scary, suspense sound effects, like the music from the movie Jaws.” She added that she shouted at him: “Please stop or I will actually hit you soon.”

Shortly afterwards Key returned to the café, gave her two bottle of personalised ‘JK’ label wine by way of an apology, and said he “didn’t realise” he had upset her.

Following his official statement Key apologised again when he spoke to reporters at Los Angeles airport en route to Turkey. He said the hair-pulling had been “a bit of banter”, and insisted there had been “a lot of fun and games” and “lots of practical jokes” at the café. He also said that when he had apologised the waitress had told him: “That’s all right, no drama.”

National Party leader Key is currently seven months into his third term as New Zealand prime minister, having first taken office in 2008. The revelations of his hair-pulling antics come just days after his Aussie counterpart Tony Abbott downed a schooner of beer in sex seconds in a Sydney pub, and it is by no means the first time that Key has courted controversy.

In 2010 he was forced to apologise after suggesting a Maori tribe might “have him for dinner” – a gaffe he brushed off as a “light-hearted joke”. In 2012 he told students in Dunedin that footballer David Beckham was as “thick as batshit”, and later the same day he was criticised for blasting a radio presenter’s “gay red top”.