Max Key has defended his decision to pose with a cigarette in his hand, saying he is "vehemently against smoking and would never endorse it".
The aspiring DJ and Prime Minister's son copped a critical backlash after posting a topless image to his Instagram this week showing him holding an unlit cigarette.
The photo was one of a series of raunchy images taken of him for Remix magazine.
The photo sparked a social-media backlash, coming just weeks after his father John Key announced tough new anti-smoking plans.
But echoing his father's defence of the shoot, Key, 21, told the Herald he was "vehemently against" smoking, and was simply posing with a cigarette as a prop for the photoshoot.
"I've never smoked, I've never had a cigarette in my mouth, and everyone who knows me knows that," he said.
"I'm vehemently against it, so I'm not endorsing cigarettes. It's a fashion shoot and people do stuff [like that] all the time."
Asked whether it was appropriate for someone who disagreed with smoking to be snapped with a cigarette, he said: "Well, someone commented something I thought was quite interesting - the cigarette's not lit and I'm not smoking it, it's simply a prop, and I guess it's the thought of: it's something that can kill you between your fingers but you've got the power to say no.
"It's not lit, it's not in my mouth. If I was smoking it I think it's a completely different story, but an unlit cigarette, I mean people hold them all the time.
"I'm not endorsing smoking, it's part of the look of what they [Remix] were going for and what they were trying to present."
He added: "There's a lot of people being like, 'Oh smoking, blah, blah, blah', I guarantee most of them have smoked in their life. I think it's a little bit like they're just trying to find something to pick on.
"In movies all the time people smoke, or a model might have to hold a snake, that doesn't mean they like snakes, or they're endorsing snakes, it's just part of the photograph. But even Steven [Fernandez, Remix editor] and the guys at Remix they're not trying to endorse smoking, they would never encourage someone to smoke and that wasn't the point of the shoot."
Key said he had "no input" into the fashion shoot, which he described as "fun".
"I enjoyed it," he said, but admitted it took "quite a lot of training and hard work - and a bit of dieting" to get the sculpted body he shows off in the multiple topless photographs.
The snaps were released in Wednesday's edition of Remix, and Key posted an outtake to his 40,000 Instagram followers overnight on Tuesday.
It sparked outrage from some, who slammed the property and commerce student for promoting smoking.
"Why are you holding a cigarette, a couple weeks after your father's budget announced a 10% increase in cigarette prices over the next 4 years in order to act as a deterrent to smoking? Kinda weird to glamorize it," wrote one viewer on Instagram.
"I hate it because of the cigarette," wrote another. "My father is dead because he smoked," wrote a third. "Cool cigarette bro," said a fourth.
The Prime Minister jumped to his son's defence, saying the 21-year-old was "vehemently" opposed to smoking and his being photographed in his underwear holding a cigarette didn't contradict that stance.
"In the end, people when they are doing modelling shoots are often asked to do things that they don't do themselves," he said. "He is actually vehemently opposed to smoking, and to the best of my knowledge he has never smoked.
"He is certainly someone who speaks to me all the time about being opposed to smoking. But people wear all sorts of things and do all sorts of things when they are doing modelling shoots."
Mr Key said he thought the photos were "pretty cool".