Although £350m was originally earmarked for the transformation phase from the £9.3bn Olympic project, that will be required for planning purposes, Olympic Park Legacy Company (OPLC) chair Baroness Margaret Ford has revealed.
Extra investment will be required for elements such as diverting utilities and creating visitor buildings, said Ford, giving evidence to a parliamentary select committee looking into the Olympic legacy.
Committee chair John Whittingdale asked: "Should this not have been incorporated from the start?" Ford explained: "Probably at that stage it wasn't clear how much would be needed to create the kind of park we want."
She added that the OPLC was now going over the capital requirements on a "line by line basis" to verify exactly how much was needed. The money covers infrastructure such as roads and venues as well as landscape.
Parks consultant Alan Barber said: "The dedicated funding and management of the Olympic Park after the Games is critical. The park is the most important part of the legacy. The cost of the Olympics was a fiasco in Greece and Montreal and is likely to be in UK."
Negotiations are continuing on a land transfer between site owner the London Development Agency, the Government and the OPLC. A deal was originally timetabled for October 2009 and legacy planning is dependant on ownership of the park transferring to the OPLC.
CABE Space head of public space Peter Neal said: "There is immediate concern that when the OPLC inherits the park, funding is in place to manage the landscape and complete the delivery of a fully functioning contemporary park.
"The park is the biggest pay-back to local communities for hosting the Olympics and our greatest opportunity to take Britain's pedigree in great park-making into the 21st century."
The London Assembly's budget and performance committee is now carrying out an investigation into funding for the legacy of the park, which it plans to complete by December. The review included a committee meeting earlier this month at which the London mayor's Olympic adviser Neil Coleman was questioned on the budgets.
Coleman explained that he was "not surprised" Ford was "pressing the case for funding" and said he had no doubt the OPLC would be approaching the private sector, the London mayor and the Greater London Authority.