An additional 1,200 troops are to be deployed at the Olympics amid continued concern about security staffing.
Ministers took the decision this morning at a Cabinet Committee for the Olympics chaired by Prime Minister David Cameron.
Culture Secretary Jeremy Hunt said the numbers to be provided by beleaguered security firm G4S "continue to rise significantly" but that ministers would "leave nothing to chance".
The 1,200 troops to be called up were placed on standby last week.
Mr Hunt said: "Security staffing levels at venues have been kept under constant review.
"G4S numbers continue to rise significantly and we have every expectation that will continue to be the case.
"However, ministers decided that we should deploy the additional 1,200 troops that were put on standby last week.
"On the eve of the largest peacetime event ever staged in this country, ministers are clear that we should leave nothing to chance.
"The Government continues to have every confidence that we will deliver a safe and secure Games."