The G4S chief executive Nick Buckles conceded for the first time yesterday that his job was at risk in the wake of the Olympic security debacle that cost the company £50m.

While some shareholders have publicly backed him in the wake of the fiasco, citing his track record, the views of the G4S chairman John Connolly are less clear.

Mr Connolly joined the board only in June and is said by some to have been alarmed at how quickly the Olympics issues spiralled out of control, damaging the reputation of the company in the process.

An internal review headed by Mr Connolly will report back in a few weeks.

Asked if his job was safe, Mr Buckles replied yesterday: "The review is under way. It will complete in the second half of September. It would be premature to comment on that. I hope my job is safe; I have been here for 28 years. But that is a decision for the board and the shareholders."

The Olympics issue aside, the half-year results were reasonably strong.

Revenues for the six months to June were up 5.8 per cent to £3.9bn, while profit was dead flat at £236m. G4S kept the interim dividend at 3.42p.

The £50m figure for the Olympics is at the top end of the company's estimated losses for failing to recruit and train enough of the guards it had promised for the event.

As part of efforts to recoup those losses, it will axe 1,100 jobs, of which 100 are in the UK. It hopes for cost savings of £30m as a result.

G4S pledged that the same mistakes would not be repeated at the Paralympic Games.