The disgraced tech billionaire Mike Lynch is preparing to launch a High Court appeal within days against his extradition to the US, after casting doubt on the reliability of witnesses in a $5bn (£3.7bn) civil fraud case. 

The Autonomy founder insisted he will “continue to fight to establish his innocence” after losing a High Court fraud case on Friday over the sale of the software business Autonomy. The Home Secretary has approved his extradition to the US to face criminal fraud charges. 

He now has 14 days to file a request to appeal the extradition, in which he is expected to argue any case belongs in the UK. He has no automatic right to an appeal, however, under reforms introduced by then home secretary Theresa May in 2014. The process is likely to take months.

The 56-year-old also intends to appeal the civil fraud case. His lawyers said they will study the full judgment over the coming weeks, adding they noted the judge’s “concerns over the reliability of some of HP’s witnesses” and his “expectation that any loss suffered by HP will be substantially less than the $5bn claimed”. 

Mr Lynch founded Autonomy in 1996 and turned it into a FTSE 100 company before eventually selling it to Hewlett Packard for $11bn in 2011. But HP slashed the company’s value by $8.8bn a year later, claiming it found serious accounting improprieties. 

HP launched a civil case against Mr Lynch and his former chief financial officer, Sushovan Hussain, in the High Court in London in 2015 while the US filed criminal charges in 2018 and 2019.