The head of private security giant G4S admitted the company's failure to provide enough guards for the Olympics was "a humiliating shambles" as he faced a grilling from British lawmakers.
Chief executive Nick Buckles said he expected the company would eventually be able to supply 7,000 of the 10,000 staff it had promised. An extra 3,500 troops have already been drafted in by the British government to plug the gap.
But he insisted he would not resign over the scandal and said G4S, one of the world's biggest security firms, would still claim its GBP57-million ($88-million, 72-million-euro) management fee for the Olympics contract.
Asked by one member of parliament's Home Affairs Select Committee whether it was a "humiliating shambles" for G4S, with the Olympics just 10 days away, Buckles replied "I cannot disagree with you".
He also admitted that the firm had taken on the Olympics contract to boost its reputation rather than for profit, but agreed when the committee suggested that reputation was now "in tatters".
His company would not be bidding to provide security at the 2016 Olympics in Rio de Janeiro, he added.
However, amid mounting pressure for him to quit his GBP830,000-a-year job, Buckles insisted he was the "best person" to see the London contract through.
The staffing shortfall only came to his attention on July 3, Buckles said, adding: "Day by day we started to realise that the pipeline and the people we thought we were going to be able to deliver we couldn't."
He said G4S, which has GBP600 million of private sector contracts with the British government, only raised the problem with ministers on July 11 when it was sure it would not be able to fulfil the agreed quota.
"We have a significant manpower shortage against the plan. Clearly that shortage is going to manifest itself from this day forward until the Games," he said.
Buckles said G4S currently had 4,200 people working and that the "minimum we can deliver" by the start of the Games on July 27 was 7,000. But when asked whether he could guarantee they would all turn up he said "I can't, no".
G4S shares slid 6.20 percent to 238.82 pence on Tuesday on London's benchmark FTSE 100 index, which closed down 0.59 percent at 5,629.09 points. The firm's shares also suffered heavy falls on Monday.
It emerged Monday that in addition to the military support at least eight police forces have had to deploy extra officers at Olympic venues across Britain -- reportedly after employees of G4S failed to turn up to work.
The company is set to lose up to GBP50 million for failing to meet the obligations of its GBP284 million Olympics contract.
But London 2012 chairman Sebastian Coe insisted that Games security would not be affected by the G4S shortfall, pointing out that "the numbers haven't really changed".
"It's really simply about the mix of security on the park," he said.
"At this very moment our teams are working alongside G4S to ensure that they deliver as many of those guards as they possibly can."
Britain's interior minister Theresa May denied on Monday that ministers knew last year that there would be a staffing shortfall.
The extra troops pledged by the government last week brings to 17,000 the total number of military personnel lined up for security at the Games.
The first athletes and Games visitors began arriving on Monday as the Olympic Village opened in Stratford, east London.
Meanwhile a survey showed that nearly half of Britain's population believe their country is inadequately prepared for the Olympics while many have fears over security.
Of 2,000 people questioned in the Comres poll, 45 percent said they felt Britain seemed poorly prepared for the Olympics while almost 40 percent said the requirement for extra troops made them more concerned about spectator safety.
London mayor Boris Johnson admitted on Tuesday that there would be "imperfections and things going wrong" in the coming weeks, adding that staging the Games was a "ginormous" task.