Two directors at G4S, the firm which failed to fulfil its contract to provide security staff at the Olympic Games, have resigned.

Chief operating officer David Taylor-Smith and director of major events, Ian Horseman Sewell, stepped down after the company this morning announced the findings of a review into its London 2012 involvement.

But Nick Buckles has kept his job as group chief executive.

The company’s review “did not identify significant shortcomings in his performance or serious failings attributable to him in connection with the Olympic contract”.

G4S came under intense scrutiny shortly before the Games when it admitted it would fail to provide enough staff for the venues. Members of the Armed forces had to be called in at short notice.

In a statement released alongside the review findings, chairman John Connolly said: “(We have) accepted responsibility for our failure to deliver fully on the Olympic contract.

“We apologise for this and we thank the military and the police for the vital roles they played in ensuring the delivery of a safe and secure Games.

“Our review of the company’s performance on this contract has been extremely thorough and, whilst the failures are largely specific to the very special nature of this contract, we will learn from mistakes made.

“We are taking actions in relation to both the management and governance of G4S to ensure we continue to deliver the highest standards of customer service and contract delivery across the group.”