Dame Trelise's show, during New Zealand Fashion Week in Auckland, featured "70s bohemian vibes" with models wearing native American and Canadian First Nations feathered headdresses.
The garments - which have deep cultural significance - quickly drew a backlash.
This morning the designer issued an apology on Facebook, saying she didn't have ill intentions.
"I genuinely respect and honour all cultures, races and religions. It was never my intention to disrespect another culture," she wrote online, re-posting via Twitter.
"It is my hope that through my mistake and ignorance, like me, people now know and are aware of the sacredness of the headdress to native Americans.
"To those who I have offended, I sincerely apologise."
New Zealand film director Taika Waititi was amongst those offended by the move.
"I think I understand what Trelise means by '70s vibes' - a time when it was cool to be culturally insensitive and racism was super awesome. Nice throw back to better times, babe, we native people celebrate with you," he wrote on a photo of a headdress wearing model posted to the Trelise Cooper Facebook page.
Melbourne-based lawyer and journalist Di White took to Twitter to express her thoughts.
"Hey @trelisecooper, Indian headdresses are not yours to wear. This is cultural appropriation & super offensive," she wrote.
The message was re-tweeted more than 50 times.
Also on Twitter, Kiwi comedian Jeremy Elwood - who hails from Canada - made his distaste about the items known.
"@trelisecooper Actually I think you'll find those are racist, plagiarized, white trash hipster vibes. You should be ashamed."
The items being worn as fashion statements have drawn criticism around the world in recent times, notably when US singer Pharrell Williams and reality television star Khloe Kardashian were pictured wearing them.
Dame Trelise said she had seen feather headdresses worn as a "fun thing" on her travels in the US and Ibiza recently.
"It's a fashion thing and I don't mean any disrespect," she said backstage after the show.
Fashion Week managing director Dame Pieter Stewart told TV3's Firstline this morning that Dame Trelise meant no offence with the garments.
"It was beautiful to be honest," she said. "It's a beautiful culture. Designers draw their inspiration from all sorts of things and she drew her inspiration obviously from the Indian culture."
Dame Pieter said that designers from around the globe used headdresses.
In December, French fashion house Chanel caused controversy when it used headdresses and US lingerie giant Victoria's Secret apologised over its use of the items in 2012.
- By Morgan Tait of the New Zealand Herald and Nicky Park of nzherald.co.nz
