Strong leadership is still needed to ensure the long-term benefits of the London 2012 Olympics continue to be felt, according to the Government’s spending watchdog.

Focus must not be lost as so many different organisations are involved in the legacy of the �9.3 billion Olympic project, according to the National Audit Office (NAO).

Amyas Morse, head of the NAO, said: “There has been progress in setting up arrangements to strengthen co-ordination and oversight of delivery of the planned legacy of the Games.

“The Cabinet Office will now have to exercise strong leadership to ensure the longer-term benefits are delivered.”

The future of the �429 million Olympic Stadium is being finalised and it is still uncertain whether the Games will come in �377 million under budget, as estimated, against its �9.3 billion public sector funding package.

The final cost of converting the Athletes’ Village and settling outstanding contracts with suppliers will make an impact.

The cost of the Olympic Delivery Authority’s programme to build the venues and infrastructure is expected to be around �6.7 billion, compared with the �8.1 billion originally available.

Final costs will not be known precisely until 2014 but ministers are “confident” the project will come in under budget.

The success of the Games spans from the opening and closing ceremonies through to the 11 million tickets sold for the Olympics and Paralympics, the NAO said.

Mr Morse said: “Few could have envisaged how successful the London 2012 Games would turn out to be.

“The construction programme was completed on time and within budget, 11 million tickets were sold and our athletes excelled.

“Crucially, the Games passed off without major transport disruption or security incident.

“The operational costs within the 2007 public sector funding package increased markedly, including an extra �500 million needed for venue security.

“Nevertheless, taken as a whole, the Games were a success by any reasonable measure and it looks as if not all of the funding package will be used.”

Valuable skills in project management, contracting and risk management gained by officials who have worked on the Games should be deployed on other public sector projects, the NAO said.

London Mayor Boris Johnson hailed the “overwhelming success” of the 2012 Games.

He said: “The doomsters and Olymposceptics have been confounded yet again.

“This report puts into black and white the scale of the achievement in organising such a successful festival of sport, and pays tribute to the many different players who helped make the Games the greatest show on earth.

“I’m determined to build on this momentum to create a lasting legacy which benefits Londoners for generations and provides a blueprint for future host cities to follow.”

Sports minister Hugh Robertson added: “The National Audit Office report quite rightly highlights the successes of London 2012 and we are now focused on delivering a genuine and lasting legacy.”