A surprise jump in high street sales last month fuelled uncertainty over the true state of consumer spending as Britain's economic woes deepen.

The quantity of goods sold last month leapt by 0.8 per cent, even as shop prices rose at their fastest pace in a decade, official figures indicated.

The trading conditions suggested by the data confounded City predictions that sales would drop by a further 0.3 per cent, after a 4.3 per cent plunge in June. Sales growth was broadly based.

The rise came despite an average 1.6 per cent price increase, the steepest since May 1998, which was driven by a 6.2 per cent surge in the cost of food - the sharpest gain since March 1992.

The Office for National Statistics figures are bound to draw scepticism in the City as its retail sales data has been volatile in recent months, with a record rise in volumes in May followed by June's record decline.

City economists will contrast the official numbers with a brace of bleak surveys of last month's high street trading conditions from the British Retail Consortium (BRC) and the CBI.

The CBI said trading was at its worst in a quarter of a century, with 61 per cent of retailers reporting that sales in the first half of July were down compared with a year earlier, against 25 per cent reporting an increase.

At the same time, the BRC said that unpredictable weather had combined with the housing market's woes to deepen retailers' worries. On the BRC's figures, like-for-like sales, which strip out changes in retailers' floorspace, fell last month by 0.9 per cent compared with a year earlier.

Today's figures will sow doubt over the scale of any downturn. Forecasters have said consumer spending will fall next year, after rising by an average of more than 3 per cent a year over a decade-long national spending spree.

Times Recommends

• Minister in talks with Saudis to protect creditors
• Premier Inn hits back in £29-a-room row
• Bankers hit back at 'populist' bonus supertax