CNN said Mr Key had gone from "premier to playground bully".
The Daily Telegraph also published the story alongside a tweet from international relations lecturer Nick Henry who wrote: "Can anyone who sees John Key in person please give him a whack around the ear and, if he doesn't like it, six more and then a bottle of wine".
The Daily Mail's headline said Mr Key dismissed the "bizarre act" as banter.
The story appears prominently on the front of the The Guardian's website with 865 comments attached to it.
The story began: "Politicians are routinely upbraided for behaviour befitting a schoolyard, but the New Zealand prime minister has now become embroiled in a controversy that centres, quite literally, on hair-pulling."
Also picking up the story was The Hindu newspaper, which reported on the hair-pulling incident.
The Japan Times picked up on the label "schoolyard bully", in its headline.
The Australian Financial Review ran with the headline: "New Zealand's ponytail-pulling PM John Key apologises".
The story also appeared in Bloomberg and The Irish Independent, amongst others.
Key's credibility hit
Meanwhile, Mr Key's hair-pulling scandal has hurt his credibility and could land him in legal hot water, experts say.
Opposition MPs have slammed Mr Key's behaviour towards Miss Bailey as childish and an abuse of power.
Political scientist Dr Bryce Edwards said the incident would undermine Mr Key's ability to respond to bad behaviour from his colleagues.
Mr Key's National Party colleagues would give him a lot of slack but the weirdness of the ponytail-pulling was problematic, he said.
"It really relates to his main electoral asset of being down-to-earth, relaxed, jokey John Key. That has been a winning formula."
Dr Edwards said Mr Key built his brand on being "almost an anti-politician" rather than a staid statesman but whenever in future Mr Key was seen to be joking, irreverent, or earthy, many New Zealanders would instantly recall the ponytail incident.
The incident had also damaged Mr Key's moral authority among colleagues and scope for keeping his own MPs focused and away from embarrassing incidents, Dr Edwards said.
'Hostile touching' is common assault - law professor
Meanwhile, Ms Bailey could take civil proceedings against Mr Key over the hair-pulling episodes, University of Auckland law professor Bill Hodge said.
Mr Key could also be investigated for common assault for "hostile touching" if police received a complaint, he said.
Auckland University criminology and sociology lecturer Dr Ronald Kramer said Mr Key's unwanted physical actions put the vulnerable waitress in a powerless position where she was unable to "fight back".
"You have to remember this is an older white male with a lot of power doing something like this to a woman who is presumably young, in a difficult job, and presumably on low pay."
Dr Kramer said people in powerful positions such as the prime minister's often did not think about how their actions affected others.
Employment law expert Susan Hornsby-Geluk said if an employer was aware of unwanted physical attention towards one of its workers and failed to act, they could also potentially face a claim of unjustified disadvantage.
Women's rights campaigner and former National Party MP Marilyn Waring told Radio New Zealand that she believed Mr Key had broken the law.
"I'm getting tired of it being called anything but illegal," she said.
"The young woman said she felt powerless and tormented and she was reduced to tears."
Serial litigant Graham McCready says he will file a complaint with the Human Rights Commission and will take the case to court, claiming it was sexual harassment.
Mr McCready told Newstalk ZB that his action could distress Amanda Bailey but "this incident is too important, too much in the public interest for that not to happen".
In November 2012 Mr McCready took a private prosecution over donations made by Kim Dotcom to John Banks' Auckland mayoral campaign in 2011.
The parliamentary career of the former Act leader ended after he was convicted in the High Court last year for not disclosing two $25,000 donations from Mr Dotcom to his Auckland mayoralty campaign in 2010.
The Court of Appeal then quashed the conviction after the "obsessed" detective work of Mr Banks' wife, Amanda, who was stung by the trial judge's opinion of her credibility when he preferred Mona Dotcom's evidence about a lunch, which was crucial to the case.
The National Council of Women has sent an open letter to Mr Key rebuking him for his apology to Ms Bailey.
While he did apologise to her, he minimised his actions when he explained he was just "horsing around", the council said.
"You probably think that you've never touched someone in such a way before. However, this incident shows that you have crossed the line," the letter said.
National Council of Women chief executive Sue McCabe told RNZ that Mr Key used his apology to portray the waitress as uptight and oversensitive.
Opposition MPs have also waded into the controversy.
New Zealand First deputy leader Tracey Martin told RNZ that pulling a woman's hair was unacceptable behaviour from anyone, let alone the leader of a country.
"If he doesn't understand where people's personal boundaries lie, we've got some rather serious problems I think. It's childish behaviour."
Labour's deputy leader Annette King told RNZ Mr Key abused his power and had a moment similar to former Cera chief executive Roger Sutton.
"Roger Sutton said that he was just a friendly guy, that he just used to put his arms around people, that he didn't mean any harm and we know what happened to Roger Sutton, he lost his job."
But Cabinet Minister Jo Goodhew supported Mr Key.
"I'm sure that he regrets making this woman uncomfortable, so he has apologised," she told RNZ.
Human Rights Commissioner Jackie Blue issued a statement saying it was never okay to touch someone without their permission.
"There are no exceptions."
Mr Key is due to give a speech tonight at the peace conference along with Australian Prime Minister Tony Abbott and the President of Turkey, Recep Tayyip Erdogan.
