London Olympic organisers came in for criticism on Thursday when a government committee highlighted uncertainty over legacy and the lack of a fully-costed security plan for the 2012 Games.

The Public Accounts Committee - a body responsible for overseeing government expenditure - praised progress made on the Olympic Park in east London but warned that lack of clarity over future use of permanent venues was a concern.

The committee found that a business plan for the Olympic Park was not expected until May 2009, almost four years after London was awarded the Games. Its report also said the Department of Culture Media and Sport (DCMS) had still not produced a detailed plan for security at the Games.

"We welcome the news that construction has begun and the programme is broadly on track," Edward Leigh, the committee's chairman, said.

"Far less good is that, despite our recommendations, arrangements to manage the whole programme and the associated risks are not yet in place.

"As legacy and security requirements are firmed up and as lessons from Beijing are taken on board, the delivery bodies must keep tight control over costs and time."

The report said that completion dates for the Olympic Stadium and the Aquatics Centre had slipped by two and four months respectively, although the Olympic Delivery Authority (ODA) said it is still confident of completing all construction during 2011 in time to allow test events.

The ODA allayed concerns over the lack of a funding package for the Olympic Village and that Australian firm Land Lease, the construction partner, was still "strongly committed to the project" and confident of bank funding by the end of the year.

ODA chief executive David Higgins said the project had been scaled back to provide 3,300 homes on the Village site after the Olympics, instead of the original 4,400, but that it still satisfied the requirements of the IOC.

The report also raised doubts over the government's funding target for sport's governing bodies in order to achieve the ambitious target of fourth place in the 2012 medals table.

A 700 million-pound funding package has been promised by the government which includes 100 million from the private sector.

"UK Sport continues to plan on the basis that it will receive all of its funding up to 2012. However, there remains a risk that the 100 million pounds from the private sector will not all be raised," the report said.

"Failure to raise it could harm Britain's medal prospects at London 2012 and its plans to deliver a wider sporting legacy from the Games."

Should there be a shortfall, the report said UK Sport should develop a contingency plan that protect the funding of sports most likely to win medals.