British retail sales volumes unexpectedly rose by 1.0% in monthly terms in June, according to official figures published on Friday.
Economists polled by Reuters had mostly expected a monthly fall of 0.3% in sales volumes.
Compared with a year earlier, volumes were 4.2% higher, against economists' expectations of a 2.3% rise.
Recent updates from major British retailers have painted a mixed picture of consumer demand.
Supermarket group Sainsbury's said trading in its third quarter had improved, helped by the heatwave, while electricals retailer Currys reported "very solid" trading, with the soccer World Cup spurring demand for televisions and the hot weather causing a spike in demand for fans and air conditioning products.
However, Sports Direct owner Frasers warned it was still feeling the impact of tough trading conditions, subdued consumer confidence and industry-wide excess inventory levels.
