RETAILERS are blaming successive interest rate rises and August's unpredictably humid weather for the slowest high street sales performance since March 2003.

The figures are reported in the CBI's latest quarterly Distributive Trades Survey which show that July's unexpected slowdown in sales continued throughout August despite expectations of a pick-up.

Thirty-four per cent of firms said sales were up on a year ago while 32 per cent said they were down. The balance of plus two per cent compares with plus 24 per cent in the July survey. The plus two balance is the lowest since March 2003 when it was minus 13 per cent and sales were in decline.

Retailers rated sales as average for the time of year and they are optimistic for improvement in September.

The underlying trend in sales growth - as measured by the three-monthly average - has fallen back to where it was in April, down from the recent peaks in June and July.

All retail sectors reported some growth in the year to August with the exception of grocers, which had a particularly poor month, with sales falling at the fastest rate in 21 years.

Sales of furniture and carpets were strong for the fifth consecutive month, probably assisted by heavy discounting. Clothing sales, which are traditionally weather-related, were flat following strong growth earlier this summer.

The slowdown in sales of durable household goods, such as TVs and fridges, in July and August, could be influenced by consecutive rate rises.

Firms surveyed said they expect to reduce staff numbers a little during September. However retailers are mildly optimistic that the overall business situation will improve over the coming three months. More firms are planning to increase capital spending in the year ahead than three months ago.

Digby Jones, CBI director-general, said: "This is the second successive survey to report an unexpected slowdown in sales. It's true that the weather can influence shopping but it seems more likely that consecutive interest rate rises are having an impact on spending.

"If the Bank of England's strategy of gently slowing consumer spending is working, further rate rises could be put on hold."

First published: Sept 6