PORT Adelaide chairman David Koch has launched both barrels at forward Jack Watts for snorting a legal substance off a woman's chest, describing the act as "the height of stupidity" and "simply brainless".

Watts was videoed snorting a white powder known as Wiesn Pulver, which consists of menthol, sugar and glucose.

PLAY AFL FANTASY Make your team now

The incident took place at Oktoberfest in Germany last October while Watts was on holidays but circulated on social media on Sunday.

Koch didn't hold back in his assessment of the vision.

KICK-IN KINGS Who takes the responsibility at your club?

"Just the height of stupidity," Koch told radio station FIVEaa on Tuesday.

"Yes, it was on holidays, yes, it was at Oktoberfest … and it was a consensual act between two adults, but having said that, putting yourself in that position is utter stupidity.

BEST FORWARDS We rank every club's attack

"It was simply brainless.

"We’re not hiding from it.

STRONGEST MIDFIELDS Every club's engine room ranked

"It’s a terrible reflection on not only him but it’s a terrible reflection on the club, the playing group, our members - we’re embarrassed.

"For a bloke to do that, it’s inexcusable."

WHO MAKES FINALS? Do the 2019 Ladder Predictor

The Power are investigating the matter and are yet to announce any sanctions against Watts.

The AFL is also conducting its own inquiries.

CASE FOR THE DEFENCE We rank every club's backline

Koch said Watts had improved his behaviour since the footage was taken four months ago.

"Remember it happened last October," Koch said.

FUTURE PICKS Who you should barrack against in 2019

"He has made a lot of behaviour changes over the last four or five months.

"I’d absolutely throw the book at him if I had my way. I’ve got to say, this is last October.

WHO'S LEFT YOUR CLUB? All the latest retirements and delistings

"We have seen since he came back for pre-season a marked difference in his attitude, in his behaviour, which has been terrific."

It's been a difficult past few months for Watts, who had private text messages leaked to social media in October last year.

FULL FIXTURE Every round, every game

Former Power captain Travis Boak said Watts had worked hard to get himself back on track.

"After everything that came out with the text messages, he knew he needed to make some changes in his life," Boak told FIVEaa on Monday night.

"He's was making some positive changes and he was taking some steps forward, we understand that and we've seen it.

"For this to come out, as in incident back in October, it's hard for him knowing he's made steps forward.

"We just now support Jack as best we can and make sure his mental health is looked after."

A remorseful Watts told reporters on Monday that the video was distributed without his contest.

"It's a pretty shocking look," Watts said.

"I'm really obviously disappointed with myself and can imagine how my parents and my sisters watching a video like that, it's not a great feeling.  

"Obviously just the pain and the burden I've caused to the club and the supporters and my teammates and coaches, that's probably what hurts me the most.

"I've made a lot of changes since the video, with my life, for the positive and looking forward to continuing that."

Watts has played 172 games since being the No.1 draft pick in 2008 by Melbourne.