The security budget to patrol Olympic venues is expected to rise by at least £275m to almost double the original estimate, according to people familiar with the situation.
In addition, the number of military personnel it is estimated will be needed for patrolling duties has gone up by 25 per cent.
The Home Office and the Ministry of Defence are now working on the basis that 7,500 military personnel will be required, as opposed to 6,000 a month ago. This is on top of the recruitment of up to 5,000 specialist military personnel for air defence, maritime and other duties.
Including private security guards, the number of security personnel being recruited to patrol Olympic venues is now expected to be 23,700, which includes enough staff to cover illness and absence. The government had originally allocated £282m for venue security, assuming that only 10,000 personnel would be required.
Ministers will use the general Olympic contingency budget of £2.7bn to cover the cost increase. The government will provide an update when it publishes its latest quarterly report on Olympic preparations on Tuesday. “It is pretty fluid,” said one person with knowledge of the situation.
The increase in military personnel is intended to boost public confidence in the security operation.
Paul Deighton, chief executive of the London organising committee (Locog), told MPs in November that using the military was “a very attractive option” which would improve the quality of security for visitors.
G4S, the private security company, has been asked to increase by fivefold the number of security personnel required since it was contracted by Locog in March. It will now supply “in the order of 10,000” staff directly, according to a security industry executive.
The company is already helping to recruit at least 6,000 personnel through Bridging the Gap, a scheme that trains higher education students for jobs in the security sector.
It is understood that G4S has renegotiated its contract with Locog but it remains unclear whether these additional costs will be reflected in the quarterly Olympics budget update.
A spokesperson for G4S said the company was talking to the government and to Locog “about a new provision” but that the final number has not been signed off yet.
The Home Office said the government, Locog and G4S were working towards finalising the Olympic security venue requirements, and that the MoD was fully involved. The MoD said “no final decisions have been taken by ministers on the extent of armed forces support for Olympic security”.