The figures from Auckland CBD group Heart of the City show an average loss of $85,000 per customer-facing business.
Heart of the City chief executive Viv Beck says businesses are going to need a lot of help to recover.
"What more evidence is needed that Auckland and its city centre are facing a disproportionate impact from COVID-19? Business and sector groups like ours have been calling for targeted support for a very long time and it’s needed now.
"These are not just numbers, they represent thousands of hard-working people, their staff, their families, their health - sympathy for Auckland must be backed up with tangible support."
Auckland, New Zealand's largest city, has been hugely impacted by mass closures under an extended alert level 4 - which required all non-essential businesses to shut up shop for almost six weeks. The city is now at level 3, meaning some businesses can open - but only for contactless takeaway and delivery.
"The figures quoted for the Auckland economy as a whole do not reflect the reality for many businesses," Beck said. "The city centre has a diverse mix of businesses, many of whom can operate successfully remotely and there are some very good news stories amongst them."
But she acknowledged many of those businesses simply can't operate in an alert level 3 environment, causing "severe" impacts.
"The Government must be more proactive and give businesses as much certainty as possible, including what financial support will be available at level 2.
"It's too late to wait until the next alert level announcement on October 4 to know."
She noted there's a risk of many businesses failing if they're not given certainty.
"It will mean job losses, a reduced tax-take and higher costs related to unemployment," Beck said. "It will also mean the investment in grants hasn't been maximised.
"Time is of the essence to preserve businesses, jobs and the soul of our city.
"Whilst there are actions underway to support recovery, including event planning, destination marketing and other initiatives to bring people back, more needs to be done, and central Government funding and support is needed."