Denton Wilde Sapte (DWS) has won a joint instruction from five central and local government bodies to help divide £160m of investment into Thames Gateway transport.
Dartford and Gravesham borough councils, Kent County Council (KCC), the Department of Communities and Local Government and the Department for Transport have instructed the firm to advise on how the five entities can work together on the Northfleet Site.
Around half of the funding for the scheme will be public, while the other half is slated to come from a levy-based system.
"If it doesn't come we've got to ensure a way for the authorities to deliver the infrastructure," said head of planning Stephen Ashworth, who is leading the DWS team.
DWS is the only firm to have been instructed so far and is likely to be on board for at least six months.
The instruction came on the back of work with KCC on the adjacent Eastern Quarry site.
This is part of a wider eight-year programme that is likely to include new junctions on the A2, a partly guided bus system, new traffic management and link roads.
Ashworth is assisted by procurement associate Mark Bassett, who joined DWS six months ago from the Office of Government Commerce.