US computer giant Hewlett-Packard (HP) has re-stated the 2010 accounts for Autonomy Systems Ltd (ASL), the UK software company it acquired in 2011, cutting revenues for the year by 54% and operating profit by 81% according to the latest filing at Companies House.

In 2010 ASL's accounts, which were audited by Deloitte, showed profit after tax of £105.7m and revenues of £175.6m. In the restated version, prepared by HP's auditors EY, these figures are shown as £19.6m and £81.3m respectively. In the Companies House filing for ASL, EY states: 'We have not been able to obtain sufficient appropriate audit evidence to provide a basis for an audit opinion.'

In a statement, HP said: 'These restatements, and the reasons for them, are consistent with HP's previous disclosures regarding accounting improprieties in Autonomy's pre-acquisition financials. The substantial work necessary to prepare these accounts has revealed extensive accounting errors and misrepresentations in the previously issued 2010 audited financial statements, including the exact problems previously identified by HP.'

HP and ASL have been locked in dispute since HP paid $11.1bn (£6.8bn) for the company in 2011 and then went on to take a $8.8bn (£5.4bn) writedown on the purchase. HP has accused Mike Lynch, Autonomy's founder former chief executive of 'serious accounting improprieties', a claim which Lynch has strongly disputed. The Financial Reporting Council and the Serious Fraud Office have both launched investigations.

HP has indicated that many of the accounting issues relate to 'to the overstatement of revenues in Autonomy's US operations,' and include revenue being recognised for products where payment is unlikely to be made and incorrect identification of products purchased. Lynch has claimed that much of the discrepancy between what Autonomy's annual results suggested the company was worth and what HP now believes it should be valued at are down to differences in accounting rules between GAAP and IFRS.

The former Autonomy management team said in a statement: 'We continue to reject these allegations by HP. Given the size of HP's writedown, we are very surprised by the small size of the adjustments in ASL that are attributed to the ongoing accounting dispute, which represent a few per cent of group revenue. We know even these include revenue that will be recognised at a later time, under HP's new approach.'

The Companies House filing also shows that HP has submitted a claim to HMRC for around £38m of overpaid tax relating to the Autonomy purchase.