G4S has revealed its failure to uphold the contract to provide security at the 2012 London Olympic Games cost the company £50m.

The losses are at the top end of the company's initial £35-50m estimate, and have subsequently dragged down its profits by 60 per cent. Its half-year pre-tax profits have fallen from £151m to £61m on the Olympic contract loss but turnover increased by 5.9 per cent to £3.9bn.

The company's contract, worth £248m, was to supply 10,400 security guards to the 100 Olympic sites in the capital and across the rest of the country.

However, G4S admitted less than a month before the games were set to begin that it had failed to recruit and train enough security guards for the event, forcing the government to turn to the military for the extra staff.

The company's chief executive Nick Buckles had previously apologised for what he said was a 'humiliating shambles,' and added that G4S would pay the military personnel for their service. He is due to appear in front of MPs a second time to talk about the Olympics contract next month.

G4S said in a statement that it provided 8,000 staff during the games, and had managed to deliver 83 per cent of contracted shifts. The company also said there would be no staff shortages for the Paralympics, which begins on Wednesday.

Written and presented by Alfred Joyner