Former Autonomy boss Mike Lynch is to summon Hewlett-Packard chief executive Meg Whitman to the UK "to explain herself", after she accused his business of cooking the books.
The British entrepreneur claimed that Ms Whitman's sums "simply do not add up" and that there is no way the accounting improprieties that are alleged to have taken place at Autonomy (LSE: AU.L - news) could lead to the $8.8bn (£5.5bn) writedown HP booked this week.
American giant HP bought Autonomy for $11.1bn in August 2011 but has now claimed that the British software company, which specialises in searching texts, voicemails and video, had used serious accounting improprieties to wilfully misrepresent its business and inflate the price tag.
"When we show that everything was fine, then there is a very, very serious question for HP.
"Why did it go and tell investors that it was taking [this] writedown over concerns relating to $100m of revenues?"
HP claims that Autonomy registered slow-growing hardware revenues, which account for between 10pc and 15pc of its $1bn-a-year turnover, as faster-growing software sales. It has also criticised Autonomy for including in its revenue figures sales of products to wholesalers, or "resellers", regardless of whether or not those resellers managed to sell them on to a customer.
While Mr Lynch admits to some of these practices , he is adamant that they were fully disclosed in Autonomy's annual report and that the company operated within International Financial Reporting Standards at all times. It was "inconceivable" that HP did not know Autonomy sold hardware, he said.
"How do you get from $100m to $5.8bn? ... The [company] has fallen apart in their hands. What they are trying to do is hide behind $100m of questionable numbers rather than [admit to] the real reason. They have had to write it down because they lost all the management and talent, and in a software company, that's key," he said. "I'm not going to be a scapegoat to cover that one."
The Cambridge-educated scientist admitted that someone at Autonomy could have committed fraud without him or the company's auditors, Deloitte, being aware. But he ruled out any wrongdoing that would have made a "material" difference. "You can never be sure but Autonomy had good financial controls," he said.
Mr Lynch, who first learned of the accusations when they were made public, has not yet hired a lawyer and has had no contact at all with HP since June. He said he was focused on "trying to find out what HP is trying to say and making sure that it is shown to be incorrect".
The likely legal battle will put a dent in the $800m Mr Lynch pocketed from the sale of Autonomy. But he is unlikely to use the remaining proceeds to buy Autonomy back, even though he could do so at a fraction of the price he sold it at. "Never say never, but there are other interesting technologies out there. I love the technology [at the heart of Autonomy] but the business has not been well looked after."
HP declined to comment beyond its initial allegations.