The bank said new mortgage commitments typically exhibit a seasonal pattern.
Since the data collection began in 2013, new commitment values for January have been lower than for other months of the year, with the exception of 2020.
Compared with January 2022, total new commitments decreased by $1.9b (40.7 per cent) from $4.7b.
There were 8680 new mortgage commitments in January, down 39.2 per cent from 14,282 in December - the lowest number of new commitments in a month recorded since this data series began in 2014.
In comparison to January 2022, the number of new mortgage commitments fell 27.9 per cent from 12,033.
A total of $0.6b of new commitments were to first home buyers in January, a decrease of 21.8 per cent compared with January 2022.
There were $1.7b of new commitments to other owner-occupiers, down 44.4 per cent from one year ago, and $0.4b were to investors, down 47.2 per cent over the same period.
The share of lending to first-home buyers with high loan-to-value (LVR) ratios of over 80 per cent increased from 33.2 per cent in December to 36.3 per cent in January.
Meanwhile, the share of lending to other owner-occupiers with high LVRs rose from 3.1 per cent to 3.4 per cent.
The average value of new mortgage commitments across all borrower types fell 10.8 per cent from $358,563 in December to $319,700 in January.
The average loan size across all borrower types fell 17.8 per cent annually, the bank said.