The head of G4S today insisted he was the right man to make sure the firm delivered as many Olympic guards as possible, despite the on-going security debacle.

Nick Buckles said he was sorry and deeply disappointed after the firm, which is running the £284 million contract for Games security, failed to meet its targets.

He is under pressure to quit his £830,000-a-year job over the fiasco, which has resulted in the emergency deployment of soldiers and police officers and seen £400 million wiped off the market value of G4S.

The military is having to provide extra personnel in London while Strathclyde Police will take over security at Hampden Park after G4S admitted it could not train enough workers in time for the games. Eight other police forces are providing similar cover in other parts of the UK.

Asked by Labour MP David Winnick if it was a "humiliating shambles for the company", Mr Buckles said: "I could not disagree with you."

And asked if he agreed the reputation of G4S was in tatters, Mr Buckles said: "At the moment, I would have to agree with you."

He insisted the firm has had a good reputation "over the years", but added: "At the moment, it's not a good position to be in."

Mr Buckles said he told organiser Locog on July 3 that his firm experienced a shortfall over the weekend, in part due to its scheduling system not working properly.

It was monitored daily but it was not until an Olympics Security Board meeting, chaired by Charles Farr on July 11, that the firm said it was not going to meet its contract obligations.

Mr Buckles said G4S took on the Olympics contract to boost its reputation.

"Financially, it's not a huge issue for us in improving our profit."

But he insisted the £50 million loss the firm now faces was not insignificant, saying it was a "huge amount", representing 10% of its annual £500 million profit.

"It was a hugely important contract," he said.

Mr Buckles added there had been "exclusive management focus on this contract for two years".

It was a separate subsidiary within the firm, with a management team and a project board to review its progress every month, he told MPs.

G4S is now aiming to provide a minimum of 7,000 security guards, Mr Buckles said.

He said it was a "complete and utter shock" when he was told on July 3, while on holiday in the US, that there would be problems delivering the contract.

He returned to the UK the same day, he said.

Asked about staff not turning up, he said: "Our normal show rate is about 90%."

But he said it was not an issue of people being told to turn up and not arriving.

"Our problem at the moment is a shortage of staff," he said.

"We just don't have the staff.

"That shortage is going to manifest itself from today to the Games."

Police officers drafted in to fill the gaps in security for Olympic events in Scotland will work overtime and could be brought in on their day off.

The security firm confirmed yesterday that officers from nine police forces, including Strathclyde Police, would join 3,500 troops brought in to close a short-term gap in numbers.

Assistant Chief Constable Fiona Taylor, who is in charge of Glasgow's Olympic preparations for Strathclyde, said the force would send a bill for the extra police work to the Home Office.

She told BBC Radio Scotland: "We are certainly not having to cancel leave at this point in time but we are looking at all other options - bringing people in on their rest days and indeed offering people overtime to cover these duties.

"What I should say at this point in time is that we are accounting for this extra policing activity very closely and at the end of the Games we will be submitting a bill for that extra policing activity down to the Home Office, because clearly we don't think it's right that the taxpayer in Strathclyde, or indeed Scotland more nationally, should foot the bill for another agency's inability to deliver a service."

Speaking on the Good Morning Scotland programme, she added: "We are working very closely and on an ongoing basis with the London Organising Committee of the Olympic and Paralympic Games (Locog) and G4S to understand exactly what the situation is with the G4S staffing position.

"What we are actually doing at the moment is supplementing G4S numbers at the Olympic hotels within Glasgow to ensure that we are not compromising the safety and security plan at those venues."

She would not reveal the number of officers involved but insisted none of the extra activity would have an impact on local policing.

"What we have always done and what we do on a day-by-day basis in policing is work with a number of contingencies", she said.

"I can reassure the communities within the Strathclyde Police area that none of the additional activity that we will be carrying on around the Olympic Games will inhibit our ability to keep them safe and secure locally."

She added: "It's absolutely critical for me that the Olympic Games pass off safely and securely up here."

Other police forces involved with providing security include Dorset, Hertfordshire, Northumbria, South Wales, West Midlands, Thames Valley and Greater Manchester.