HP has sued Automony founder Mike Lynch for $5.1 billion - half of what the tech firm paid for the British software maker two years ago.
HP bought Autonomy for $10 billion in 2011, when it was in the middle of being reworked from a PC maker to an IT services firm by then CEO Leo Apotheker.
After Apotheker was ousted, current CEO Meg Whitman continued with the Autonomy purchase. However, HP soon thereafter wrote down $8.8 billion on the deal, pinning $5 billion of that on accounting issues at Autonomy.
Two months ago, the Serious Fraud office dropped an investigation into the aquisition - though cases remain open in the US.
HP has rekindled the battle on these shores by filing suit on Monday.
An HP spokesperson told Bloomberg it was directed at Lynch and former CFO Sushovan Hussain, and alleges that "they engaged in fraudulent activities while executives at Autonomy".
In response, Autonomy's former management team has said they will countersue for 100 million "for loss and damage caused by false and negligent statements made against them by HP on 20 November 2012 and in HP's subsequent smear campaign," the Bloomberg report added.
Lynch denies accounting impropriety, blaming HP for Autonomy losing value.
