Britain's Serious Fraud Office says it might be using an Autonomy product, Introspect, as a document management tool as it formally confirmed that it had opened a criminal investigation into how the British company was sold.

The agency said it was now making inquires to establish whether it could continue its probe into allegations that the US PC and printer maker HP was duped when it bought Autonomy for $11.1 billion in 2011.

"The SFO is keen to ensure that there is now no conflict of interest or perception of such a conflict, and it is obliged as a first step to make inquiries to ensure that it can continue as the investigating body," it said in a statement.

HP said in a regulatory filing that the SFO had joined the US Department of Justice and the UK accounting regulator, the Financial Reporting Council, in opening a probe into Autonomy.

HP, which bought Autonomy in a bid to make it the centrepiece of a shift into software, stunned the market a little over a year after the purchase by writing off three quarters of the British firm's value.

It alleged "some former members of Autonomy's management team used accounting improprieties, misrepresentations and disclosure failures" to inflate the company's apparent worth.

Autonomy has denied the allegations.

Autonomy's former chief executive Mike Lynch, an Irish-born mathematics whiz who led the firm when it was sold, has blamed the fall in its valuation on HP's mismanagement. He has hired one of London's top law firms, Clifford Chance, to contest the allegations.