Apple is expected to give further details today of the share options scandal that has enveloped it. Shares in the Silicon Valley heavyweight dropped yesterday on reports that records of a crucial board meeting which approved a controversial share option scheme for the chief executive Steve Jobs were falsified.

Coupled with talk that Mr Jobs has hired his own lawyer, the man who represented the disgraced Wall Street banker Frank Quattrone, concerns about Apple's stock option practices saw shares in the company lose 5% in early trading yesterday.

A spokesman for Apple refused to comment, merely repeating what the company said in October when the results of its own internal inquiry were released. "We said at that time and we still say that we are providing all details regarding the investigation to the SEC," he said.

Apple is one of more than 160 US firms that have come under scrutiny for backdating stock or share options. The scandal of backdating, by which the exercise price of share options was set with the benefit of hindsight at favourable levels, has already led to the exit of several senior executives.

Apple carried out its own review of its stock option accounting using a committee made up of outside directors with independent counsel and accountants. Having sifted through 650,000 documents and interviewed present and former executives and advisers, the investigation essentially exonerated Mr Jobs, saying it found no misconduct by any present member of the management team. The committee's report said Mr Jobs was aware that favourable grants had been selected "in a few instances", but "he did not receive or otherwise benefit from these grants and was unaware of the accounting implications".

The 7.5m options under review were given to Mr Jobs in October 2001. He surrendered the options before they were exercised.

According to press reports yesterday, however, Apple has discovered that records of the full board meeting authorising those options were falsified.

Apple will update Wall Street on the situation with the release of its annual report, which was originally scheduled for December 14. It must be published by the close of business today.