As 3,500 more troops are drafted in to police the Olympics, a G4S duty manager tells Channel 4 News that some staff contracted to provide security have not been trained or deployed.

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The company contracted by London 2012 organisers Locog to provide security staff for the Olympics, G4S, has been unable to supply the 10,000 trained staff it was contracted to deliver - 16 days before the start of the Olympics.

The most recent staffing levels were apparently released to the Home Office late last week and because they were so far below the required level, Theresa May has begun talks with the Ministry of Defence over whether it could provide security personnel.

A G4S source also told Channel 4 News the company has also been contacting ex-police officers to try and increase numbers.

Defence Secretary Philip Hammond will announce more details about the extra troops on Thursday, the Home Office said.

A spokeswoman went on: "We have agreed to offer help to G4S by revising the level of military support.

"The government are committing £553 million for venue security and we remain confident that we will deliver within budget."

She added: "The focus of the government and everyone involved is on delivering a safe and secure Games."

Penalty fine

The military is already providing up to 13,500 staff for the games, supporting the police and venue security. If they are all called on to back up Olympic staff, they will be providing a total of 17,000 personnel.

Locog originally contracted G4S to provide 2,000 security guards out of the 10,000 required. But when Locog re-estimated the total number needed to 23,700, G4S agreed in December to supply 10,000 personnel total out of 23,700. The new contract is worth an estimated £284m.

Channel 4 News understands that G4S are subject to a penalty fine per venue, per day if they ultimately fail to meet the agreed staffing levels and that senior managers have been demoted as a result.

In a statement, G4S said it accepted that the government had decided to organise additional staff.

"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," said a spokesman.

A duty manager contracted by G4S to work on the Olympic site told Channel 4 News that delays in training and vetting staff had resulted in the company being far behind schedule.

"Staff taken on don't yet know the first thing about any of the procedures, and that poses a huge security risk. How can a risk management company not have any continuity plans in place for the Olympics?," the manager said.

Some staff were told that the company was waiting for security clearance, but then the SIA, which manages private security licensing, had no record of their applications, Channel 4 News was told.

"It's been absolutely diabolical from start to finish," she added.

At a recent Public Accounts Committee hearing on Olympic costs, Liberal Democrat MP, Ian Swales criticised the amount of money made by G4S in its Olympic contract: "I feel like issuing a press release to say "The first winner of Olympic gold in 2012 is G4S." It feels as if there is a massive profit margin; it is public money."

A spokesman for London Mayor Boris Johnson said: "The Mayor takes the issue of Olympics security extremely seriously.

"Having the finest, bravest servicemen and woman in the world at our disposal during the Games should be a source of great comfort."

But shadow Olympics minister Tessa Jowell said it was important to know "whether this affects army commitments elsewhere, which units are providing people and what terms and conditions are given for those who will likely lose periods of leave".