Supermarket group Sainsbury’s has unveiled a leap in interim profits and said customer numbers have surged,highlighting how effectively it has responded to tough retail conditions.

However the grocer also cautioned that grocers’ pace of grow is likely to slow as food price inflation falls.

The retailer notched up an 18.5% increase in underlying pre-tax profits to £307m in the 28 weeks to October 3, when turnover rose 3.7% to £11.16bn. Like-for-likes, excluding fuel, advanced 5.7%.

Chief executive Justin King said that weekly customer transactions now stand at 18.5m, up by 800,000 on last year, and the grocer is well placed following its £432m fundraising in June to speed up growth plans.

The retailer reported that non-food sales — a strategic priority — were growing at 2.5 times the rate of food. Online food sales rose by 20% and an etail food offer was launched in July.

King said: “As we enter the second half we expect the economic environment to remain challenging and market growth to slow due to reduced price inflation.

“We remain confident that our universal customer appeal means we are well positioned to perform in this environment. In addition, the acceleration of our strategy will deliver long-term growth and value.”