The head of G4S is under pressure to quit his £830,000-a-year job as he prepares to face questions from MPs over the Olympics security debacle.
Nick Buckles, the firm's chief executive, will be asked how G4S, the world's second largest private sector employer, has failed to get enough security guards for Games venues when more than 20,000 have already been accredited.
He will face questions from Labour MP Keith Vaz, chairman of the Commons Home Affairs Select Committee, who accused his firm of letting the country down last week.
Mr Buckles, 51, would be entitled to £20 million in pay and benefits if he loses his job over the fiasco which is expected to cause his firm £50 million of losses on the high-profile contract. Meanwhile, more than £400 million has been wiped off the firm's value since Wednesday and Home Secretary Theresa May has been forced to appear before MPs twice in the last week over the row.
G4S repeatedly assured ministers it would "overshoot" its recruitment targets and only admitted it would fail last week, she said on Monday.
A further 3,500 troops who were drafted in to close the gap left by G4S have now been joined by officers from eight police forces after security staff failed to turn up at venues.
Mrs May said that despite more than 20,000 security staff being accredited, G4S had problems with scheduling and "getting staff to the venue security tasks". Some staff no longer wanted the work, she added.
But Mrs May came under fire from Labour for not knowing how many staff G4S would now provide after the Home Secretary told MPs the "precise balance of the number who will be provided will become clear over the next few days". But she denied the firm had "deliberately deceived" the Government.
A total of 3,500 troops, many of whom will be billeted at Tobacco Dock near Wapping, east London, were brought in to make up the shortfall, boosting the number of servicemen and women involved in Games security to 17,000 last week. Hundreds of officers from eight forces have now also been drafted in to fill gaps.
Venue security was being tightened "before the full complement of accredited staff have been assigned", a G4S spokesman said. "This situation is being rectified over the coming days, which should lead to the withdrawal of police officers from those roles assigned to private security."