A further 1,200 military personnel are being deployed to help secure the 2012 Olympics in London following the failure by G4S to provide enough private security guards, the government has said.
The extra personnel, who were put on standby last week, have been drafted in amid continuing fears that the private security contractor's handling of the £284m contract remains a risk to the Games as Friday night's opening ceremony approaches.
Ministers took the decision on Tuesday morning at a cabinet committee for the Olympics chaired by the prime minister, David Cameron.
The culture secretary, Jeremy Hunt, said: "On the eve of the largest peacetime event ever staged in this country ministers are clear that we should leave nothing to chance. The government continues to have every confidence that we will deliver a safe and secure Games."
Paul Deighton, chief executive of Locog, the London organising committee, said that the guards would be subject to regular on-the-job checks and training "to make sure people are up to scratch".
The news of the extra training came after the Guardian reported that security staff training to use x-ray scanners to detect explosive devices were being allowed to "cheat" their way through tests aimed at checking to find out whether they could identify dangerous items. Deighton said the decision to deploy "roving teams" followed advice from military commanders.
"We will have a series of roving teams to go around and train people on the job to make sure people are up to scratch and performing," he said. "It is not a question sending people out untrained."
The decision to enlist the extra military personnel had been taken to "de-risk" the security operation, he said. He added that G4S's performance had been "a huge disappointment" and that the Games would be safer with more soldiers carrying out duties due to have fallen to G4S.
The security firm has supplied fewer than 6,000 guards despite a contract to provide more than 10,000.
Deighton said: "You can't be absolutely certain about anything with a temporary workforce, so we simply want to substitute a temporary workforce with a permanent, reliable, workforce that we get with the military.
"We have an excellent plan. It remains in place and … is working very well. What has happened is that the private, man-guarding, aspect of the force turned out not to be reliable, and we have substituted it with the much more reliable and better trained military force. So the net outcome is, you end up with an even better security force."
The move was endorsed by the Metropolitan police assistant commissioner Chris Allison, who is the national Olympics security co-ordinator. "[I'm] very happy with it," he said. "It helps de-risk and it gives flexibility. We don't know what's round the corner, and it gives us an extra 1,200 skilled personnel we can deploy."
The military had been expecting the this mobilisation, which will mostly consist of Royal Marines, and people from 16 Air Assault Brigade. They were put on standby last week because of the continuing difficulties at G4S.
Commanders had wanted the 1,200 extra staff brought into the fold immediately rather than wait until just three days before the opening ceremony.
Hunt said on Tuesday that G4S numbers were continuing to "rise significantly", but the Ministry of Defence and officials across Whitehall appeared to have lost confidence that the company could fulfil its commitments.
Visitors to Olympic venues have been greeted by large numbers of military personnel, but the organisers said police and soldiers had been briefed to be very welcoming.
"Our aim is to ensure the sport takes centre stage," said Allison. "This is a sport event with security overlaid, not a security event with sport."
He said 12,500 police officers would be deployed to help secure the Olympics and crowded areas of London, and at other sites on peak Games days; 9,500 of those would be in London.
Announcing the mobilisation of the extra troops, Deighton revealed the depth of the disappointment of Games organisers with G4S. "We signed a contract with the biggest security company in the world, whose biggest customer was the UK government. They continually reassured us they had the capacity to deliver. It was obviously a huge disappointment … This is all about their poor performance in a very strong contract."
