Apple has been added to Nasdaq's list of "delinquent companies", a step that moves the company closer to a potential de-listing from the stock market following the emergence of irregularities linked to stock option grants.

The company said last week that it would be forced to delay its third-quarter results as it presses on with an internal probe into the granting of options.

That statement followed a warning from the iPod maker earlier this month that it will probably be forced to cut earnings for the past four years - during which it reported more than $3 billion in profits.

Apple has now been added to the list Nasdaq publishes each trading day of companies that are non-compliant with the market's listing standards.

To read the current list click here.

Apple had said it had sought a meeting with Nasdaq to discuss the options issue. The fate of that request is unknown.

Apple and Nasdaq were unable to comment immediately.

The computer company suffered further embarrassment today when it admitted a report of labour conditions at its iPod plant in China found employees worked more than 60 hours a week a third of the time, breaking Apple's working code.

The internal probe found that in many cases workers were exceeding the company’s limits for overtime, which specify a maximum of 60 hours or six days a week.

It also found that in a few cases workers had been made to stand at attention for disciplinary reasons and that conditions at two leased dormitories were overcrowded.

However, Apple said it found no evidence of forced labour or other serious violations. It added that it was taking immediate steps to deal with excess overtime and other problems.

The computer company had sent an audit team to a China plant that makes iPods, the leading digital music players, after reports of poor working practices.

In a statement Apple said: "Our investigation found that our top iPod manufacturing partner, Foxconn, complies with our supplier code of conduct in most areas and is taking steps to correct the violations we found."

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