Hewlett-Packard Co. said accounting errors at Autonomy Corp. have led it to cut reported 2010 revenue at the software maker’s largest unit by 54 percent, adding fuel to a legal dispute over its purchase of Autonomy.

Autonomy Systems Ltd.’s 2010 operating profit was restated as 81 percent lower, according to U.K. regulatory filings by Hewlett-Packard. The computer maker, which bought Autonomy for $11.1 billion in 2011 and later took an $8.8 billion writedown on the purchase, also said it has shared information from its investigation with regulators in the U.S. and U.K.

Hewlett-Packard, based in Palo Alto, California, is facing shareholder lawsuits claiming current and former top executives knew, or should have known, about shoddy accounting practices at Autonomy before buying the company. Hewlett-Packard Chief Executive Officer Meg Whitman says the company was defrauded by Autonomy, while Mike Lynch, founder of the U.K.-based software maker, has denied any impropriety.

“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,” Hewlett- Packard said today in an e-mailed statement.

Two Units

The Autonomy unit reported profit of 105.7 million pounds ($172.3 million) for the period. After “correction of fundamental errors,” the impact of “transfer pricing revenue,” and accounting policy changes, that total should have been 19.6 million pounds, Hewlett-Packard said in the filing.

The filings, made Jan. 31, represent the two largest of Autonomy’s eight U.K. units and included a restatement of 2010 accounts, Hewlett-Packard said.

Former managers of Autonomy disputed Hewlett-Packard’s findings. The restatements are primarily the result of changes in accounting policy that Hewlett-Packard implemented after the acquisition, and because of actions it has taken in moving revenue between locations in an attempt to avoid paying some taxes in the U.K., a spokesman for the former managers said in an e-mailed statement.

“We continue to reject these allegations by HP,” according to the statement. “Given the size of HP’s writedown, we are very surprised by the small size of these adjustments in Autonomy Systems Ltd. attributed to the accounting dispute, which represent a few percent of group revenue.”

Revenue Recognition

Robert Willens, a New York-based tax and accounting consultant, said that if the restatement just disclosed is based on revenue-recognition timing rules, it doesn’t support Hewlett- Packard’s writedown of the acquisition. If it’s based on evidence of revenue that never existed, it may help Hewlett- Packard’s assertions.

“From what I can gather, it’s a timing dispute and a question of not whether the revenue existed but when it was properly recorded,” he said. “If there were true sham transactions that the revenue was attributable to, that would support a writedown.”

Hewlett-Packard has provided information to the U.K. Serious Fraud Office, the U.S. Department of Justice and the Securities and Exchange Commission regarding accounting improprieties, disclosure failures and misrepresentations by Autonomy, before and during the acquisition, the U.S. company said in the filings. It also said there may be additional errors not yet identified.

“Given the volume and magnitude of the above errors, it is possible that further errors may remain undetected,” Hewlett- Packard said in the filing.

Apotheker’s Deal

Hewlett-Packard bought Autonomy in a deal engineered by Whitman’s predecessor, Leo Apotheker. A year later, Hewlett- Packard under Whitman said it would take the writedown, largely because of what it said was falsified accounting at the software maker.

Separately, Hewlett-Packard today said that it had nominated all of its existing directors -- including activist investor and interim chairman Ralph Whitworth -- for re- election. All were renominated for a vote to be held at the company’s annual shareholder meeting on March 19, the company said in a filing today with the SEC. Bloomberg News reported on Jan. 10 that the company was planning to retain its current board makeup.

Whitman’s total compensation for fiscal 2013 rose to $17.6 million, according to the U.S. filing. That was up from $15.4 million in the previous year.