Figures from the Office for National Statistics showed a 0.5% volume decrease in sales between July and August.
August sales were 0.4% higher than in August 2009.
Volumes sales in predominantly food stores were 3.5% below last year, while predominantly non-food stores were 4.6% up.
The seasonally adjusted value of retail sales for August was 1.9% higher than August 2009, while the quarter to August showed an increase of 2.3%.
The ONS has adjusted the previously reported volume figure for July from a 1.1% increase to 0.8%.