The sales momentum in Westpac's home loan business in Australia is evident in the monthly banking statistics published by APRA on Friday and covering the month of December 2009.Westpac reported growth in its home loan portfolio of 1.6 per cent for the month and compared with growth in home lending, across all banks, of 1.0 per cent. The bank's mortgage book increased 5.0 per cent over the December 2009 quarter compared with banking system growth of 3.3 per cent. The decision by Westpac in early December to lift variable interest rates on home loans by significantly more than the rise in the RBA cash rate will presumably curtail this industry-leading rate of growth, leaving room for some other banks to fill the void.National Australia Bank, playing catch up in the home loan segment, underperformed in December with growth of only 0.6 per cent, though above average growth in lending in October and November means NAB ranked second over the December quarter for growth in home loans.Bendigo and Adelaide Bank reported a fall of 1.8 per cent in the size of its home loan book in December 2009. The bank's home loan book has declined most months in 2009, continuing a trend established following the merger of the two banks in late 2007.Bank of Western Australia, now owned by Commonwealth Bank, has found its own momentum in the home loan market, reporting growth over one month of more than four per cent and growth over three months of more than nine per cent, or more than double the industry average.