Sephora did not have permission sweep confetti into drains, Auckland Council says, following an investigation into the French cosmetics giant's store launch.
But there is not enough evidence for a prosecution.
The French company came under fire during its Queen St opening when staff were filmed sweeping confetti into stormwater drains.
At the time Mayor Phil Goff called it "unacceptable waste" dumping, and said it was "totally untrue" the council would have granted permission for such an activity.
Sephora hit back at the claims, with a spokeswoman saying they'd worked with Auckland Council "for its approved event permit to ensure the confetti was safe for the environment".
"The confetti used was bio-degradable, water soluble and plant based," she said.
Auckland Council events manager David Burt today said it had completed its review and concluded events company Darkhorse, which was contracted by Sephora and held the permit, was permitted to use the confetti but not to sweep it into drains.
Representatives explained to the council some confetti began to dissolve in the rain and staff on-site swept it away to prevent injury to pedestrians.
"Darkhorse has acknowledged that sweeping the confetti waste into the drains was not appropriate and has apologised for its actions," Burt said.
There was not enough evidence to determine how much waste was washed down the drains, and this meant a prosecution was unlikely to be successful, Burt said.
The company had committed to review its processes and would at using spill kits and wet vacuums at future events.
The council's events team would closely monitor the company in future, Burt said.
New Zealand Māori Council executive director Matthew Tukaki, who filmed the actions, said he saw Sephora staff sweeping paper confetti into drains, along with taking paper testers, used for fragrances.
Mayor Phil Goff tweeted at the time: "Unacceptable for anyone, particularly a major retailer, to be polluting our waterways. Totally untrue that council granted permission for such behaviour – waste must be collected and disposed of responsibly."
Darkhorse has been approached for comment.