Santander saw its profits for 2017 fall after it was hit by the collapse of Carillion.
The UK arm of the Spanish banking group issued its quarterly management statement showing profit before tax down 5 per cent year-on-year to £1.8bn.
Nathan Bostock, Santander's chief executive officer, said:"I am pleased to report a solid performance for 2017 with Santander UK continuing to demonstrate resilience. We delivered higher income, cost discipline and balance sheet strength, while making steady progress towards meeting our strategic and operational goals.
"Profitability was impacted by the losses incurred on our exposure to Carillion, which offset otherwise strong growth. We are working closely to support customers who have suffered from their collapse
"We have continued to improve our offering for customers, with products and services tailored to suit their needs and delivered in a way that works for them."
Mortgage lending increased slightly from £154.3bn to £154.9bn, with the proportion of lending on the Santander standard variable rate decreasing from £7bn to £5.5bn.
The bank said 15 per cent of borrowers are now on its SVR, compared to 19 per cent a year ago. This was driven by customer refinancing and sentiment over expected future interest rate movements, Santander said.
The mix of mortgage borrowers remained broadly unchanged, with 44 per cent of loans being home movers, 33 per cent refinancing of existing borrowers, 19 per cent first-time buyers and four per cent buy to let.
Santander said it continues to focus its BTL book on non-professional landlords, as this segment is closely aligned with mortgages and accounts for the majority of the volume in the buy-to-let market.
In 2017 the bank completed 7,500 buy-to-let mortgages, representing 6 per cent of the value of its new business flow, at an average LTV of 61 per cent.
Interest-only mortgage balances decreased £3.2bn to £49.1bn, while buy-to-let mortgage balances increased £0.2bn to £6.8bn.
Santander recently replaced its SVR for new borrowers with a follow-on rate (FoR) which is currently cheaper and tracks the base rate. The FoR is set at 3.25 per cent above the Bank of England base rate.
The existing SVR, which is set by the bank, is currently at 4.7 per cent, meaning the FoR offers better rates for the moment.
The bank also gave customer satisfaction statistics, with 63 per cent of retail customers satisfied with the service they receive from the bank.
Mr Bostock said that this was "broadly in line with the average of the three highest performing peers".