Taranaki-based TSB Bank maintained its share of the mortgage market and the yield its earns from its core product in New Zealand's crowed mortgage market during the December quarter. The rate of growth in TSB's profit, however, slowed markedly.The bank's December 2005 quarterly disclosure document shows its mortgage book grew by NZ$69 million to NZ$1.49 billion over the quarter. Using Reserve Bank of New Zealand figures as a proxy for the market, that puts its share at 1.29 per cent, little changed from a market share of 1.28 per cent at the end of September. That was still slightly down on the 1.31 per cent market share at the end of 2004 when its mortgage book stood at NZ$1.3 billion.Net profit for the quarter increased by 6.4 per cent to NZ$7.5 million, putting its net profit for the nine months ended December up 13 per cent to NZ$24.0 million compared with the corresponding nine months a year earlier.The latest quarter's profit growth, while in line with growth in assets, compares with growth of 18 per cent recorded in the September quarter and the 13 per cent increase in the June quarter.TSB managing director Kevin Rimmington said the slowdown in profit growth partly reflects the fact that December is the bank's quietest month of the year."The market remains competitive, probably more so than it's ever been in the mortgage area. Lending is slowing slightly but there are still excellent growth rates for the year."TSB's total assets grew by 11 per cent to NZ$2.5 billion in the nine months ended December.TSB and the government-owned Kiwibank are the only locally -owned banks operating in New Zealand.