G4S stands to lose up to £50m as a result of the London Olympics security fiasco, the private security firm says.
The company's chief executive, Nick Buckles, has apologised after 3,500 soldiers had to be drafted in to bolster guard levels for the Games.
Home Secretary Theresa May was forced to ask the Ministry of Defence to provide more troops after the contractor admitted it did not have enough staff.
The company has a £284m contract with the Government to provide 13,700 security guards for the Olympic Games, but only 4,000 guards are trained and ready.
G4S said it would see a loss on the contract of between £35m and £50m.
"G4S accepts its responsibility for the additional cost of the increased military deployment resulting from the shortfall in workforce delivery," the company said in a statement.
Mr Buckles said: "We are deeply disappointed that we have not been able to fully deliver against our contract with the London Organising Committee of the Olympic and Paralympic Games (Locog) and that it has been necessary to call upon the additional military personnel."
The Government found out about the shortfall on Wednesday and quickly had to boost the number of soldiers working on the Games to 17,000 - almost a fifth of the entire Army.
Shares in the company were down 1.5% when markets closed on Friday, meaning more than £150m has been wiped from its market value over the past two days.
Mr Buckles added: "In partnership with the military and Locog, we are working flat out around the clock to resolve the situation.
"We are determined that together we will deliver a successful and secure Games. I would like to thank the members of the current security workforce who are already on the ground securing many of the Olympic sites across the country."
John Connolly, who joined G4S as chairman last month, said: "Since I joined the company I have seen the huge focus which has been placed on delivering this contract.
"It is a significant disappointment to everyone at the company that we have fallen short of our obligations. I know however that everyone involved throughout G4S is doing everything they can to improve the situation and we are putting every resource behind this effort."
Mr Buckles has been called to evidence to the Home Affairs Select Committee on Tuesday as part of the panel's inquiry into Olympic Security.