More than 20,000 G4S guards have been accredited to provide security for the Olympics but the firm is unable to get them to turn up at venues, Theresa May has said.
The under-fire firm, which has seen more than £400 million wiped off its market value since the debacle, repeatedly assured ministers it would "overshoot" its recruitment targets and only admitted it would fail last week, the Home Secretary told MPs.
A further 3,500 troops who were drafted in to close the gap have now been joined by officers from nine police forces after security staff failed to turn up at venues.
Mrs May said G4S have more than 20,000 accredited Olympics staff but the issue was scheduling and "getting staff to the venue security tasks".
Asked why, she said: "I think there are a number of things. The first is about the scheduling problems G4S themselves have had.
"And there will be individuals who are now saying they do not wish to take that work up - that may be for a number of reasons."
But she could not give exact figures for how many guards would now be supplied by G4S, saying only that the "precise balance of the number who will be provided will become clear over the next few days".
Mrs May denied the firm had "deliberately deceived" the Government, telling MPs that the firm made clear that the problems with "workforce supply and scheduling" only emerged "over the last couple of weeks".
She also denied ministers had been told by G4S before last week that the firm would fail to meet its targets.
A total of 3,500 troops, many of whom will be billeted at Tobacco Dock near Wapping, east London, were brought in to boost the number of servicemen and women involved in Games security to 17,000 last week. Hundreds of officers from nine forces have now also been drafted in to fill gaps.