John Armitt, chairman of the Olympic Delivery Authority for the 2012 London Games, has told a parliamentary committee that he cannot rule out the need to spend the £2.7 billion emergency fund set aside to pay for cost overruns.

The news comes as a further blow to organisers after the existing budget was trebled to almost £10 billion earlier this year.

"If you say to me 'do I guarantee absolutely that this is going to happen' - no, I could not do that," he said.

He added that this strategy was "realistic [to achieve] the absolute maximum that we need for the Games''.

David Higgins, chief executive of the ODA, told the government's Department for Culture, Media and Sport Committee that there were no immediate plans to ask for more cash.

"We expect a substantial part of the contingency to be spent on a program of this complexity," he said. "Clearly we want to minimize the expenditure.

"[For] a project of this size and scale, with all the risk attached to it, [this] is a prudent contingency at this stage in the project.

"We do not intend to go back to the Funders Committee (chaired by Chancellor Alistair Darling) for further allocations in the next six months. That is for certain.''

Paul Deighton, chief executive of the 2012 Organising Committee, said deals with three domestic sponsors will be finalised early next year to add to those already in place with Lloyds TSB, EDF Energy, Adidas and Deloitte.

"By March we expect 40 percent of our [£650m sponsorship funding] total to be already raised in cash and in kind," he said.

The final figure is less than that raised for the upcoming 2008 Games in Beijing.

"The most significant difference with the Beijing Games is that many are state sponsors so they do not go through the same processes as we are doing and, of course, there is a large economy," Deighton added.

Jonathan Symcox / Eurosport