Retail sales fell at their fastest pace in 2-1/2 years in November, after food retailers saw sales dive, and mild weather hit demand for winter clothes, a survey by the Confederation of British Industry showed on Monday.

The CBI's monthly distributive trades survey's reported sales balance fell to -19 in November from -11 in October -- the lowest since March 2009 and well below economists' forecasts for a reading of -13. It was also much worse than retailers themselves had expected.

The expected sales balance for December fell to -6 from +4 in November.

The CBI said the decline in sales volumes was driven by pressure on grocers, specialist food and drink stores, department stores and clothing.

The balance of sales reported by grocers fell to -21 in November, the lowest in three years, and highlighting the pressures on household incomes in the face of high inflation, low wage growth and a rapidly deteriorating economic outlook.

The relatively mild weather this autumn has hit clothing stores particularly hard, and retail sales are down year-on-year for the sixth month in a row, said the CBI's chief economic adviser Ian McCafferty,

Retailers may be hoping that shoppers will loosen their purse strings in the run-up to Christmas, but consumers are likely to remain cautious about spending, given the uncertain economic outlook.

(Reporting by Olesya Dmitracova, writing by Fiona Shaikh)