In the years since the financial crisis, the mutual has increased its market share rapidly, as the big banks were cutting back.
But those rivals are now recovering and lending more.
As a result the Nationwide’s gross mortgage lending fell from £14bn in the first half of 2013 to £13.1bn in the same period of 2014.
“Over the past couple of years, the banks were not consistent competitors in the market, and we benefited from that a year ago,” said finance director Mark Rennison. “They are back today on a more consistent basis, which was always bound to happen. But while they are back, we’ve still outperformed the market in terms of our natural share of the market.”
Nationwide’s share of net mortgage lending came in at 24.8 per cent, while it increased its share of the current account market to 6.6 per cent.