The Bank of New Zealand says it is not part of the problem of risky mortgage lending which is currently preoccupying the Reserve Bank.
On Wednesday, the Reserve Bank said it will require the banks to hold more capital against their riskier loans from the end of September, which will result in an average increase in their capital, held for housing of about 12%.
That will make such loans more expensive for the banks.
Risky lending has grown from 23% of new mortgage lending in October 2011 to 30% now.
BNZ chief executive Andrew Thorburn said his bank's lending to those with less than a 20% deposit amounts to only 15% of its total mortgage book.
"Our quality of the assets, our loan book is very, very strong if you look at the amount of loans that are impaired or stressed and if you look at the right-offs that we actually incur, they're very, very low and that's despite quite a lot of pressure in the last few years with the recession and higher unemployment."
Mr Thorburn said BNZ is prudent and sensible when making loans of more than 80% because it understands the risks and it requires a higher debt servicing ratio for customers.
He said the bank also applies a low equity or interest rate premium at 80% and above.