The change has opened up the market but as the number of potential buyers has increased, so too have prices, said Paul Reid, managing director of apartment specialists Iconicity.
The cost of properties in some apartment buildings in central Auckland had risen by almost a third since January.
"It's more money chasing the same amount of stock," said Mr Reid.
One couple who took advantage of the new ASB criteria bought a 32sq m apartment in central Auckland for $160,000 with a deposit of $32,000.
Under the old criteria, they would have needed $80,000 equity.
"It just doesn't make it an affordable option," said Iconicity head of sales Oliver Mitch.
ASB's general manager of retail products and strategy, Shaun Drylie, said the bank considered several factors when lending for apartments, including a borrower's ability to make repayments, their deposit, and the size of the apartment and building.
Professor Bob Hargreaves from Massey University's property study section said relaxed lending rates could "ratchet up" prices.
And he warned the servicing costs of the bigger loans would make apartment living difficult, especially for young people just joining the market.
Although ANZ, BNZ, Westpac and Kiwibank said they had no plans to follow ASB, most said they regularly reviewed lending criteria.
But Mr Reid said they were already matching ASB.
"It's a case-by-case situation but certainly most banks will let an owner-occupier buy an apartment with a 10 per cent deposit, that's absolutely no problem. And on the smaller ones, other banks ... in order to keep market share, are matching what ASB are offering."
Increased apartment prices have added to already soaring Auckland house prices, which have risen 124 per cent since 2000, Auckland Council said yesterday.
Low interest rates and population growth were behind the increase, and house prices are expected to remain stable, said the council's chief economist, Geoff Cooper.
The numbers
50,796 apartments in Auckland City
$250,000 or less - price of many 1-bed flats in the city
50 per cent deposit often demanded on sub-45sq m apartments
$550,00 median sale price in Auckland
Source 2006 census, Statistics NZ