Fears of a sharp slowdown in consumer spending in America became reality last night after Apple gave warning that it expected sales and earnings to slow this year.

The computer and electronics giant issued a statement after Wall Street had closed, forecasting that revenues would come in below expectations for the current quarter.

Dealers marked down Apple shares by 8 per cent in after-hours trading.

They were already bruised from a volatile day in which the Dow Jones index swung almost 500 points.

The slide in Apple shares came despite a 57 per cent jump in profits during the first quarter of the year.

Peter Oppenheimer, the chief financial officer of the Cupertino-based firm, said that despite having revised down the forecasts they still reflected rapid growth at the company.

“Our business performed very well in the December quarter and we remain very confident in our products and our strategy,” Mr Oppenheimer said.

He said that Apple expected earnings per share in the current quarter of 94 cents, well below the $1.09 that analysts had predicted.

Revenue is also expected to be lower, coming in at around $6.8 billion (£3.5 billion) compared with the $6.99 billion forecast by Wall Street.

Mr Oppenheimer also warned that profit margins would fall in the second quarter of the year to 32 per cent from 34.7 per cent achieved during the previous three-month period because of higher expenses related to stock-based compensation and slower software sales.

Even before the company’s forecast, Apple shares had fallen 3 per cent, in line with the rest of the market. Shares of technology giants such as Google and Microsoft fell on the Apple news.

“As Apple goes, so goes the Nasdaq,” said Joe Saluzzi, co-manager of trading at Themis Trading in Chatham, New Jersey.

He described the firm as a bellwether for the tech and retail industries. “The market is using it as a proxy. I think Apple is too big a name in tech land . . . it’s a little bit retail, it’s tech oriented and that’s the problem.”

Later comments from Steve Jobs, the chief executive of Apple, that the $1.58 billion-worth of net profits during the three months to December 29, up from $1 billion for the same period the year before and representing the best figures in the group’s history, fell on deaf ears.

Wall Street is scared that the turmoil in the credit markets is spilling over into the wider economy and will hit consumer demand, a key driver for US economic growth.

Fears that the US was on the brink of a recession were stoked yesterday after America’s Federal Reserve slashed interest rates by three quarters of a percentage point, the biggest reduction in the cost of borrowing for 26 years.

Apple’s stellar results for the first quarter of the year, with sales at $9.61 billion well above Wall Street expectations – were boosted by the success of Macintosh computers and iPod digital music players.

First-quarter sales were 35 per cent higher than for the same period the year before.

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