A new report from the National Audit Office (NAO) has found that the final cost of hosting the 2012 Olympic and Paralympic Games is "inherently uncertain".

In the same week the government and Olympic Delivery Authority said that preparations are 'on budget', the NAO said plans were needed to cover any additional "unknown risks". The NAO report into the Games' preparations - the fifth such study it has carried out - said there was no guarantee remaining contingency funds will cover unforeseen requirements.

It has urged the government to develop plans to meet such needs if the £974m contingency in the public sector funding package cannot provide. NAO head Amyas Morse said: "The final cost of the Games to the taxpayer is inherently uncertain and as the Games near there will be less flexibility to make savings in response to any unforeseen financial pressures."

Meanwhile, the report also questioned whether the government will be able to fufil its legacy ambitions amid a "natural priority" to deliver a successful Games. It also found that, while the Olympic Delivery Authority is on track to deliver its construction programme, timings for some elements are becoming "tight for handover" to organisers.

Image: Tom Last/ODA