A shortfall in private sector funding for the 2012 London Olympics has created "a key area of uncertainty" in planning the event, the public spending watchdog warned on Friday.

Calling for the overall budget urgently to be finalised, the National Audit Office reveals the London bid had assumed the private sector would fund £750m ($1.4bn, €1.1bn) of infrastructure and regeneration work but says ministers now accept there is "little prospect of securing significant private sector funding" for the Olympic Park.