Among the technologies acquired by HP in the Autonomy takeover was AR platform Aurasma

HP has filed suits at a San Francisco federal court against both former Autonomy chief executive Mike Lynch and ex-chief financial officer Sushoven Hussein, as the latter tries to block HP's settlement of three shareholder lawsuits regarding its takeover of Autonomy in 2011.

The technology behemoth's shareholders had claimed that its current and former officials, including chief executive Meg Whitman, had not properly managed the purchase and were seeking damages. The parties agreed a deal earlier this year, as a part of which they elected to pursue Autonomy's former executives in a legal challenge over its pre-acquisition valuation and the methodology used to arrive at it. Hussain is attempting to block this settlement, challenging it in a California court, but HP refutes both his claims and his involvement.

"The notion that [Hussain] should be permitted to intervene and challenge the substance of a settlement designed to protect the interests of the company he defrauded is ludicrous," suggested HP in its court filing. "The shareholder plaintiffs who originally sued HP’s directors and officers now agree that Hussain, along with Autonomy’s founder and chief executive officer, Michael Lynch, should be held accountable for this fraud."

The US Department of Justice and the Financial Reporting Council and Serious Fraud Office in the UK have opened investigations into HP's accusations, which both Lynch and Hussein deny.

"This breathless ranting from HP is the sort of personal smear we've come to expect," said a spokesperson for the former Autonomy management in a prepared statement. "HP has struck a corrupt and collusive settlement to try to bury the truth rather than face a court.

"Quite simply we are asking for discovery and facts; they are trying to hide them – that's what separates us and [Whitman]."

The dispute centres over HP re-valuing Autonomy at $8.8bn （？5.2bn） less than the $11.1bn （？6.8bn） that it paid for it in 2011, having purportedly discovered 'numerous accounting irregularities' in the period leading up to the takeover. In an open letter to shareholders, Lynch has accused HP of 'selective disclosure', as well as claiming that HP was well aware of Autonomy's accounting methods at the time of the acquisition.