Nearly a quarter of a million people surveyed by ASB say they have less than $1000 in savings.
That was among the key findings of ASB's financial wellbeing study of half a million customers, which also found more than a third were living pay-day to pay-day.
The study also found more than a third of customers frequently had balances of less than their average weekly expenses, and 15 percent of customers always spend more than 80 percent of their income.
"The fact that more than a third of people have less than a single week's expenses available to them and almost half have less than $1,000 in rainy day savings rings alarm bells for me. This puts them in a potentially vulnerable position," ASB chief executive Vittoria Shortt said.
The study also found the average overall financial wellbeing of New Zealanders has improved since the first COVID-19 lockdown, largely because they are spending less.
"While it's pleasing to see that 87 percent of customers who needed COVID-19 relief during the pandemic have been able to go back to previous payment arrangements, we're continuing to support more than 5,000 personal and business customers with COVID-19-relate support."