Gross mortgage lending for the six months to June 30 2017 was £3.4bn, compared to £3.5bn for the first six months of 2016.
Net lending, the figure after considering repayments of existing mortgages, was - £2m, compared with £521m for the first six months of last year.
This means the overall size of Yorkshire Building Society mortgage book fell by £2m in the first six months of the year.
In the results statement, the building society said this was “in line with our plans to take a measured approach to lending in a competitive market and an uncertain economy.”
Deposits also fell at the building society, to £28.9bn at 30 June, compared with £29.1bn at the end of December 2016.
The Yorkshire said it expects interest rates to stay low, adding: “We need to balance our savings inflow against the amount of mortgage lending we do.
"Market rates have continued to fall, and we have had to manage the rates on some of our savings accounts to ensure we are not paying too much above market rates.”
The building society's net interest margin was virtually unchanged on last year at 1.2 per cent, compared with 1.21 per cent in 2016.
Statutory profit before tax fell to £92.3m compared with £99.9m for the same period last year.
The Yorkshire said: “This is in line with our expectations given current market conditions and continues to represent a healthy and sustainable level of profit.”