Clothing underpinned sales in May, resulting in a 0.5% like-for-like uptick on a year earlier, according to the BRC KPMG Retail Sales Monitor.

Total sales were up 2%, against a 3.4% rise in May 2013, with clothing the best-performing category, posting its highest growth since December 2011. By contrast food sales faltered, reporting a decline in total terms.

The three-month average year-on-year change for food was down 0.2% in total, turning negative for the first time since records began in 2008, excluding Easter distortions. For non-food, the three-month average was 4.3% up, ahead of the 12-month trend of 3.8%.

David McCorquodale, head of retail, KPMG, said: “The grocers appear locked in a race to the bottom. The main barrier to recovery is now the grocers’ battle over price. The deflationary effect of these prolonged discounting campaigns, while good for consumers, is feeding through to the grocers’ margins and share values.”

Meanwhile, online sales of non-food products in the UK grew 17% in May compared with a year earlier, the highest online growth recorded since BRC KPMG records started in December 2012, excluding Christmas and New Year.

In May, online sales represented 18.7% of total non-food sales in the Monitor, against 17% last year. Online sales contributed 2.1% to the growth of non-food total sales. Over the past three months, online has represented one third of the total non-food growth.

Helen Dickinson, director-general, British Retail Consortium, said: “This month sees the highest growth in online sales of clothing for five months and the proportion of purchases we are making online has grown several percentage points in a year. This also represents the highest penetration ever recorded for clothing since the inception of the online monitor. Footwear is telling a similar story.”