The security budget for the 2012 London Olympics has doubled, a British government report out overnight showed, with plans to recruit almost 14,000 extra personnel.
The operation to provide security at more than 100 venues has swollen after the decision was taken to boost staff numbers, the December 2011 Olympic Quarterly Economic Report showed.
The report stressed that the increase was not in response to a specific security threat.
The overall budget for the Games remains at 9.3 billion ($18 billion), with 528 million so far unspent.
The security cost has risen to 553 million ($1.1 billion), the figures from July to September showed, up 282 million on the 2010 spending review baseline.
Instead of the 10,000 security officers initially planned for, there will now be 23,700, with the majority coming from a private firm. The military and volunteers will make up the rest.
The government and Games organisers have gone through a detailed analysis of the number of security staff needed, Olympics minister Hugh Robertson explained.
"As a result, to ensure a safe and secure Games, they have revised the numbers of trained staff required," he said.
"We are therefore investing additional funds in providing nearly 24,000 venue security personnel plus specialist security equipment."
Meanwhile the security budget for the opening and closing ceremonies has also effectively been doubled by an injection of 41 million from the public purse.
"London's opening and closing ceremonies are a once-in-a-generation opportunity to showcase the very best of our country to four billion people around the world," Robertson said.
"To get the ceremonies absolutely right and boost the Games business and tourism legacy, we are putting additional investment into our ceremonies."
Last month, defence minister Philip Hammond said Britain was prepared to deploy surface-to-air missiles to protect London during the Games, shortly after the government rejected reports of US security fears.
"The government carried out a full review of security arrangements in late 2010 and remains confident the right plans are in place to deliver a safe and secure Games for all," the report out Monday said.
"The government's approach is intelligence-led and risk-based, giving the flexibility to respond to any changes between now and Games time.
"The planning assumption we have used throughout is that the Games will be delivered in the context of a 'severe' level of terrorist threat."
Security has been a key concern for all Games hosts and organisers since the 1972 Olympics in Munich when nine kidnapped Israeli athletes and four of their captors from the Palestinian Black September group, as well as a German policeman, were killed in a gun battle.