Results for the six months to the end of June revealed a pre-tax profit of just over £1 billion, broadly in line with the same period a year earlier.
Adjusted profit rose 13 per cent to £1.1bn and net interest income, a key measure, grew 8 per cent to £1.9bn.
But the bank pointed to “greater uncertainty” and downside risks in its outlook for the end of this year and the beginning of 2018.
It told investors: “The labour market remains strong, but higher inflation, largely from the lower value of sterling, is now reducing households’ real earnings.
“This is likely to result in lower consumer spending growth which, when combined with a potentially more challenging macro environment, adds a degree of caution to our outlook.”
Chief executive Nathan Bostock said: “Santander continues to make strong progress against the backdrop of a changeable operating environment.
“We performed well in the first half of 2017 – with net interest income growth, ongoing cost discipline and good credit quality.”
Retail banking current account balances were up £1.5bn and commercial banking deposit balances rose by £900 million.
Meanwhile, the wider Banco Santander business posted a better-than-expected 37 per cent jump in second-quarter net profit to €1.75bn (£1.5bn).