ASB's September quarter disclosure document shows its mortgage book grew $1.07 billion to $26.11 billion in the three months.

That took its market share to 23.54%, up from 23.37% at the end of June and 22.67% at the end of September last year, using Reserve Bank of New Zealand figures as a proxy for the market.

The growth doesn't appear to be at the expense of profitability which rose 19.1% to $106 million compared with the September quarter last year.

ANZ/National Bank's market share eased slightly during the quarter, although its mortgage book grew $1.22 billion to $38.4 billion.

That puts its market share at 34.62% at the end of September, down from 34.7% at the end of June and 35.24% at the end of September 2004.

ANZ's net profit rose 7.8% to $194 million in the September quarter compared with the same quarter last year.

Among the smaller banks, HSBC, like ANZ, continues to lose market share as a result of taking over the AMP mortgage book. Its mortgage book fell $31 million to $2.14 billion in the three months ended September, its market share easing to 1.93% from 2.02% at the end of June and 2.38% at the end of September last year.

However, HSBC's net profit jumped 33.2% to $6.76 million in the quarter compared with the September quarter last year.

The government's Kiwibank isn't too far off taking over from HSBC as New Zealand's fifth largest home-lending bank, having already overtaken TSB Bank.

Kiwibank's mortgage book grew $286.9 million to $1.81 billion in the September quarter, raising its market share to 1.63%, up from 1.42% at the end of June and 1.22% at the end of September last year.

Kiwibank's profitability isn't suffering any either: net profit jumped more than three-fold to $2.24 million in the latest quarter compared with the September quarter last year.

As previously reported, Westpac's market share at the end of September was 19.4% while TSB's was 1.28%. The other two home lending banks, BNZ and Superbank, have yet to release their September quarter disclosure documents.