UK retail sales in September showed the lowest growth of the year so far as the warm weather stunted sales of autumn and winter collections.

The British Retail Consortium (BRC) KPMG Retail Sales Monitor recorded September UK retail sales up 0.7% on a like-for-like basis against a 1.5% increase last September.

The monitor recorded a total sales increase of 2.4% in September against a 3.4% increase last year.

Sales were driven by electricals as consumers bought the new iPhone, while Tesco launched its Hudl tablet in the month. Leisure goods sales also boosted monthly sales mainly due to the launch of video game Grand Theft Auto V, while there was “strong” demand for children’s footwear and clothing in the ‘back to school’ period. Homewares also recorded a positive performance, as TV show The Great British Bake Off helped cookware sales.

But food was the hardest hit, which revealed a like-for-like fall for the second month in a row.

KPMG head of retail David McCorquodale said: “These figures are a reality check and will make retailers nervous as we enter the run-up to Christmas. Unseasonably warm weather stifled sales of autumn and winter collections in September and the recovery in home-related items flattened. Consumers are still cautious about spending and are reluctant to restock their wardrobes with winter woollies until the weather cools.

“Sales of children’s clothing and shoes put in a strong performance, but this surge is likely to simply be a hangover from the traditional back to school spending spree. The slowdown of the food and drink sales performance reflects the battleground for market share among the grocers.”

But it was a different story online as sales of non-food products in the UK surged 13.4% in September against last year on a weighted basis, the new BRC-KPMG Online Retail Sales Monitor revealed.

In September, online sales represented 17.5% of total non-food sales, the highest penetration rate of the year. Without online, clothing and footwear sales would have recorded a fall in September.

BRC director-general Helen Dickinson said: “Online sales were again the stand-out performer, growing by double digits, and contributed strongly to non-food sales such as electricals and leisure items.

“The online penetration rate, or share of the market, reached a record level in September. To succeed today retailers are investing not only in an outstanding product offering but also in ever-evolving ways to reach customers in the online world.”