However, the bank's 4.99% one-year fixed "special," which garnered significantly more than $200 million in new business between April 26 and May 31, is likely to boost its June quarter figures.

The loan-to-valuation ratio (LVR) table in Kiwibank's March quarter disclosure statement shows its mortgage book grew by $225 million to $11.43 billion in the three months, down from the $260 million growth in the December quarter.

It's also Kiwibank's smallest quarterly increase since the December quarter of 2010 when its book grew by $194 million.

In the year ended March, Kiwibank's mortgage book grew $1.1 billion, slightly more than the $1.03 billion growth the previous year.

Assuming Reserve Bank data will prove a reasonable proxy for the mortgage data shown in banks' disclosure statements, that means Kiwibank accounted for 17.6% of mortgages written by registered banks in the three months ended March and its share of market rose to 6.66% from 6.58% in December and 6.17% in March last year.

It doesn't appear Kiwibank's growth is due to any relaxation in credit standards: the part of its books with LVRs of 80% or less is where most of the growth came from, $227 million, while mortgages with LVRs of 90% or more shrank by $37 million.

Mortgages with LVRs of 80% or less account for 82.2% of Kiwibank's mortgage book while loans with 90% or more LVRs account for 3.4%.

Kiwibank's net profit for the quarter jumped to $23 million from just $1 million in the same quarter last year which had been hit by a blowout in charges for bad loans due to Christchurch's February 22, 2011 earthquake.

Charges for bad loans in the latest quarter fell to $9 million compared with $26 million in the year-earlier quarter. A 25% jump in net interest income to $65 million also boosted net profit in the March quarter.