More troops may be needed to help with security at venues such as the Olympic Stadium, left, during the Games
British Armed Forces have been told they may need to provide an additional 3,500 troops to assist with security during London 2012, amid fears the private contractor G4S may not be able to provide enough trained staff in time.
G4S is contracted to provide 10,000 guards and is being paid £284m to do so. The armed forces are providing 13,500 personnel, which may now rise to 17,000 to meet any shortfall from G4S. A further 7,000 security staff will be volunteers, but coordinated by G4S.
The company is the world's largest private security firm and also runs prisons and immigration removal centres in the UK.
It is now considering whether it can bring in staff from other parts of its business.
G4S said it had "some issues in relation to workforce supply".
A spokeswoman said the company had accepted "that the government has decided to overlay additional resources."
She added: "This has been an unprecedented and very complex security recruitment, training and deployment exercise which has been carried out to a tight timescale.
"We have encountered some issues in relation to workforce supply and scheduling over the last couple of weeks, but are resolving these every day and remain committed to providing a security workforce for the start of the London 2012 Games."
The Government claims that this different balance in numbers between G4S and the armed forces poses no risk to Olympic security, as the total numbers will still be the same.
It does mean that a greater number of guards will be dressed in military uniform, which is unlikely to go unnoticed by Olympics attendees, in a games at which the potentially overbearing security presence has already been a major talking point.
Air-based missile defence systems will sit on civilian roofs and some of the navy's largest battleships are in position in east London and at the sailing venue in Weymouth, Dorset. G4S said its planning with organising committee Locog and other security agencies allowed for "a variety of contingencies which have been reviewed in the build-up to the Games".
The London 2012 chairman, Lord Sebastian Coe, has insisted several times that London will not feel like a "siege city" during this summer's Olympic Games.