Nationwide Building Society said its profit for the first nine months of the financial year edged 2% higher.
Underlying pre-tax profit increased to £883m from £866m year earlier, though statutory net profit fell to £886m, from £946m.
Profits included a £26m one-off gain from the disposal of the VocaLink business.
Gross mortgage lending of £24.1bn fell from £26.2bn, while total market share slipped to 12.2%, from 14.3%, in what the company described as competitive market conditions.
'Looking ahead, we expect the economy to continue to grow but only modestly,' chief executive Joe Garner said.
'Consumer spending, which has been a key driver of growth, has slowed noticeably, and almost three quarters of those surveyed in our Brexit consumer panel expressed concern about the rising cost of goods and services.'
'Modest economic growth is also likely to hold back the housing market and house price growth.'
'Overall, we expect house prices to be broadly flat in 2018 with perhaps a marginal gain of around 1%. We expect competition in the mortgage market to continue and we will prioritise quality over volumes in the long-term interests of our members.'