The BRC said shop prices in August were 1.4 percent lower than a year earlier, matching July's fall.

BRC Director General Helen Dickinson said intense competition among retailers and falling commodity prices were behind the decline in August.

"Annual food prices rose for a second month but once again the rise was marginal, by just 0.2 percent year-on-year, and is likely to be a temporary fluctuation in a longer-term downward trend driven by ongoing competition," she said in a statement.

Prices of non-food goods fell by 2.4 percent, a slightly sharper decrease than in July.

Britain's broader official measure of inflation, the consumer prices index, showed its first year-on-year fall in prices in over 50 years in April, and rose by just 0.1 percent in July.

The Bank of England expects inflation to pick up next year and is watching wage growth closely for any signs that inflationary pressures might strengthen.

(Reporting by William Schomberg; editing by David Milliken)

((william.schomberg@reuters.com; +44 20 7542 7778; Reuters Messaging: william.schomberg.thomsonreuters.com@reuters.net))