HP has revised financial reports for its Autonomy division after the company said that an audit turned up a number of serious accounting errors.

The restatements were revealed in UK regulatory filings made on January 31.

HP bought UK-based Autonomy in 2011 but subsequently said that an internal investigation had found Autonomy was "substantially overvalued" at the time of the acquisition due to alleged accounting fraud. HP later took a £5.5 billion write-down on Autonomy based in part on the alleged fraud.

The company has been sparring with former Autonomy CEO Mike Lynch, who has denied HP's claims.

"These restatements, and the reasons for them, are consistent with HP's previous disclosures regarding accounting improprieties in Autonomy's pre-acquisition financials," HP spokesman Michael Thacker said. "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 problems previously identified by HP."

For example, the 2010 financial results for Autonomy Systems Limited, a major division of the business, were revised to show a 54% decrease in revenue and 81% drop in operating profit, according to HP.

Given the "volume and magnitude" of the accounting errors, "it is possible that further errors may remain undetected," according to one of the regulatory filings.

The Serious Fraud Office in the UK and the US Department of Justice have both opened investigations into the Autonomy deal, which was brokered during the short and rocky tenure of former HP CEO Leo Apotheker.

His successor, Meg Whitman, has said Autonomy's information management and search software will play a significant role in HP's growth strategy.