£9.3 budget will be enough, insists Jowell

But the total cost is likely to remain at £9.325 billion because of the increasing costs of security and unforeseen events. The most detailed analysis of the capital's 2012 costs was published today following concerns raised by spending watchdogs this summer.

Experts at the Department for Culture, Media and Sport found there was an 80 per cent chance that the Olympic Delivery Authority, which is building the Games venues in Stratford, would spend only £7 billion of its £8.1 billion allocation. But the additional £1.2 billion set aside for security, the Paralympics and elite and community sports may yet need to be boosted with any savings made by the ODA.

Olympics Minister Tessa Jowell, in a written statement to Parliament, said that there had been a "thorough assessment" of all potential risks and it had been found that the budget was "consistent" with the package she outlined to MPs in March.

She said: "Months of careful scrutiny have confirmed that the ODA has the money it needs to deliver the venues and infrastructure for a terrific summer of sport."

A total of £1.2 billion has already been set aside for security in the Olympic Park and for policing during the Games. This includes a contingency of £238 million. Today it emerged all the ODA's initial £500 million contingency has been drawn to allow it to start awarding contracts - some £1 billion of work has been commissioned already with all major contracts due to be awarded by next summer.

The official breakdown shows £1.171 billion will be spent on venues - £496 million on the main stadium, £574 million on other facilities such as the aquatic centre and cycling velodrome, and £101 million on facilities outside Stratford such as the white-water canoeing venue earmarked for Hertfordshire. Some £897 million is going on transport, £1.942 billion on preparation of the 500-acre Stratford site and associated infrastructure, and £868 million on other projects in the Olympic Park. There is also a second contingency fund of just over £2 billion.

Today's figures provide the fullest financial detail released by the Government, though precise amounts for some projects have been withheld to protect the ODA's finances and to ensure commercial confidentiality.

The budget excludes the £2 billion being raised through ticket sales, merchandising and TV rights by London 2012. It also excludes the £1 billion plus incurred by the Mayor's London Development Agency.