Gross mortgage lending was £21.4bn in September, up 5 per cent year-on-year, according to UK Finance estimates.
August 2017 saw £24.3bn of lending carried out, 11 per cent higher than September 2017.
The trade body says housing market activity has built up “modest momentum” since the start of the year, helped by an increase in first-time buyer numbers.
The figures show two-thirds of gross lending, or £13.7bn, was carried out by high street banks.
High street lenders approved 41,584 house purchases in September, 7 per cent up year-on-year.
The seasonally adjusted figures for September show this group lent £7.91bn to house purchasers and £5.5bn to remortgagors.
This compares to £7.94bn and £5.16bn month-on-month, respectively.
The average mortgage in September was £184,800, down from £188,100 in August but up from £176,200 in September 2016.
UK Finance senior economist Mohammad Jamei says: “As we near the end of 2017, our data is showing that housing market activity has built up modest momentum since the start of the year, helped by an increase in first-time buyer numbers.
“Rising inflation continues to put pressure on household budgets which is impacting consumer spending. Consumer credit growth has edged up a little compared to last month, but is in line with annual growth rates over the last year.
Remortgaging approvals were 29,570, up 20 per cent year-on-year.
“Businesses remain cautious about the future amidst an uncertain economic environment, reflected by their growing deposit activity and a dip in their borrowing growth rate.”