A bitter debate over Hewlett-Packard's $8.8 billion impairment charge and allegations of fraud is already playing out in rare public form as Autonomy founder Michael Lynch and H-P volley accusations and threats through the media.

Rejecting allegations of impropriety, Lynch published an open letter to H-P's board of directors defending Autonomy's accounting leading up to H-P's acquisition and asking the board for “immediate and specific explanations” for its allegations. He demands documentation to support the allegations H-P has made publicly but has not taken to him directly. H-P fired back within hours with a public statement of its own, promising facts and debate through the legal process. The company says it looks forward to hearing Lynch and other former Autonomy employees “answer questions under penalty of perjury.”

HP says its “intense internal investigation” turned up extensive evidence of intentional measures on the part of unnamed former Autonomy senior executives to inflate financial metrics in a way that would mislead investors and prospective buyers. H-P says it has uncovered accounting improprieties, disclosure failures and misrepresentations that took place before H-P acquired the business. It is blaming those issues for $5 billion of its recent impairment, but conceding another $3.8 billion is attributable to stock performance and market factors.

If any of that is true, Lynch has a long list of questions for H-P. He's looking for the calculations used to arrive at a $5 billion impairment charge along with documentation behind H-P's assertion that hardware revenue was mischaracterized and that revenue recognition was accelerated. He asks how that never came up during due diligence, whether any of the $5 billion impairment should be attributed to operational or financial mismanagement after the acquisition, and how many people employed by Autonomy at the time of the acquisition are no longer with the company.

Lynch asks the H-P board if senior management understood Autonomy's accounting for hardware, which was governed by international rather than U.S. accounting standards, and how it was handled after the acquisition. He asks if senior executives are even aware of software revenue recognition studies that occurred as part of the pre-deal due diligence.

H-P answers Lynch only with the promise that “the matter is in the hands of the authorities,” including the U.K. Serious Fraud office, the Securities and Exchange Commission, and the U.S. Department of Justice, none of which will discuss whether they are pursuing investigations. The Federal Bureau of Investigation also says the H-P allegations represent the kind of complicated financial issues it might investigate, although it also declined to discuss whether it is opening an inquiry. H-P also promises legal action of its own against parties involved.