Kent Thamesside Delivery Board deputy chief executive Ian Lindsay said the cost of regeneration in Kent Thamesside would be around £710 million.
But the board can only realistically harness £400 million through developer contributions, he added.
The ODPM has invested £54 million to drive regeneration at a range of key sites in the area, such as Dartford, Gravesend and Ebbsfleet. "This goes some way to closing the gap but there is still a way to go," Lindsay warned.
Kent Thamesside is a significant development hub in the Thames Gateway.
"Making it happen is the purpose of the delivery board, but it comes down to money at the end of the day," said Lindsay.