Under-fire G4S chief executive Nick Buckles should stay in his job during the Olympics, Sports Minister Hugh Robertson has said.

Mr Buckles has come under pressure to quit following his company's failure to provide thousands of security guards for the London Games.

But asked whether Mr Buckles should resign, Mr Robertson said: "The important thing is that we deliver a safe and secure Games, and G4S remain a key partner in that, so I want stability at that firm, and delivery. I don't want resignations causing chaos."

But, speaking at a central London press conference, he added: "What happens to Mr Buckles afterwards is a matter for others in the post-Games environment.

"What is crucial now is that he and his organisation concentrate absolutely on delivering a safe and secure Olympics.I have confidence in their ability to do so."

Mr Robertson's comments came amid reports that a request may be made on Thursday for additional troops to plug any further gaps in security if G4S fails to deliver the necessary number of guards.

The Ministry of Defence (MoD) said contingency plans are in place to provide more troops if needed, but added that no request has yet been received.

But there are reports that a decision will be taken on whether to put 2,000 personnel "on notice to move", which would mean that they would act as a reserve force throughout the Olympics period and would not be available for other tasks.

Sky News quoted an unnamed Home Office source as saying: "The decision to put another 2,000 military personnel on notice to move will be taken tomorrow (Thursday). This comes after very intrusive examination of G4S management and while we are confident that the recruitment targets will be met, it is prudent to make contingency plans of this kind."

A Home Office spokesman said: "We have not asked the military to deploy any more military personnel beyond the 3,500 already agreed."