A criminal investigation has been opened into government electronic tagging contracts held with Serco, as well as G4S, the Serious Fraud Office (SFO) said.
An audit by accountancy firm PricewaterhouseCoopers, launched in May, alleged that overcharging began at least as far back as the start of the current contracts in 2005 but could have dated back to 1999.
Justice Secretary Chris Grayling told the two firms that an independent forensic audit was required to look at internal email trails between executives to establish what happened. While Serco agreed to take part, G4S refused.
Serco allowed a further forensic audit to take place but G4S refused to co-operate and were reported to the SFO.
More top news
Newly-unveiled UK Plastics Pact ‘unites every body, business and organisation with a will to act on plastic pollution’.
“Closing the door to the world will not stop the evolution of the world”, Mr Macron told US Congress.
Michael Seed is due to enter pleas over his alleged role in the infamous Hatton Garden heist at Woolwich Crown Court.