LONDON, Aug 20 (Reuters) - British retail sales rose twice as fast as expected last month while government borrowing posted a record deficit for a July, official data showed on Thursday 20 August.

The Office for National Statistics said sales rose 0.4 percent on the month in July, taking the annual rate to a gain of 3.3 percent -- its highest since May 2008.

Analysts had predicted a monthly increase of just 0.2 percent following an exceptionally strong June -- which was revised higher to show growth of 1.3 percent.

The ONS said the monthly gain in sales was driven by furniture and electrical goods stores. Sales in household goods stores rose by 4.5 percent on the month, the biggest gain since August 2006.

Separately, government borrowing figures were much worse than expected for July -- normally a surplus month -- underlining the collapse in tax revenues as a result of the recession.

Public sector net borrowing came in at 8.016 billion pounds, when analysts had predicted a deficit of 500 million pounds and compared with a surplus of more than 5 billion pounds last year.

The public sector net cash requirement came in at 182 million pounds when analysts ahd predicted a surplus of 6.25 billion pounds.