"If they do that, they have a chance of competing. The alternative is we will see them lose their iconic kiwi statuses."
Hallenstein Glasson chief executive Graeme Popplewell said the company had invested in revamping the Glassons and Hallensteins stores at Sylvia Park over the last month in anticipation of the Zara and H&M openings.
He said the company was preparing for increased competition but already knew what to expect.
"I think what it will do is just mean that everyone has to sharpen up," Popplewell said. "They'll bring very high standards to retail so New Zealand retailers will have to make sure that we match them," he said.
"Obviously with our Glassons business we face that competition from them in Australia, so we have some understanding as to what it means."
Other retailers such as the Warehouse have already admitted the arrival would increase competition and could prove challenging but Chan said it would be New Zealand customers that would be the winners.
"We won't have to do online shopping to access these big brands any more- they are right on our doorstep," Chan said.
"If they do well in Auckland, there is a strong chance they will open up in other big cities," she said. "The other potential side effect of them doing well would be getting more big chains like GAP, Uniqlo, Primark, Forever 21 and Next to enter New Zealand."
The arrival of British retailer Topshop in Auckland last year caused a stir, and the brand is opening a second store in Wellington in November.
H&M
• Tonight - VIP launch
• Tomorrow - Press day
• Saturday - Public store opening
Zara
• October 6 - opening