LONDON (AFP) - British retail sales fell unexpectedly in August after unusually hot weather in July had fuelled spending on food, drinks and summer clothing, official data showed on Thursday.

Sales slid by 0.9 per cent in August from the level in July, the Office for National Statistics (ONS) said in a statement.

The reading confounded market expectations for a gain of 0.3 per cent, according to analysts polled by Dow Jones Newswires, and followed a 1.1 per cent jump in July.

The ONS added that the biggest downward pressure was food sales, which sank by 2.7 percent on the month.

"The main story is that food sales fell 2.7 per cent month-on-month, reversing the sharp weather-related gains in July when people were eating out in the sunshine," said ING economist James Knightley.

Retail sales - an important indicator of consumer confidence - grew by 2.1 per cent in August compared with one year earlier, according to the ONS data. Analysts had expected a larger gain of 3.1 per cent.