Bank of New Zealand says growth in its mortgage book has slowed since the Reserve Bank's restrictions on lending to people with small deposits came into force last October.
The outgoing managing director of the bank, Andrew Thorburn, said the restrictions have had a major impact, although its mortgage book was still growing.
BNZ, which is owned by National Australia Bank, reported a 32 percent jump in first half net profit, largely due to improved revenue and lower charges against profit for bad loans.
The bank made $393 million in the six months to March, although it said its cash earnings grew at a much slower 3.4 percent pace.
The bank said the result comes despite increased regulation, strong competition and unexpected costs relating to the Wellington earthquake.
The BNZ said it increased its market share in deposits by 20 basis points with growth of $4.6 billion, or 12.4 percent, in the latest six months.
Mr Thorburn said over the last three years BNZ had pursued a strategy of growing customer deposits to reduce its reliance on wholesale funding but he said deposits were now growing more slowly.