The cost of congestion across the six counties of the East of England was £1bn in 2003 and will double to £2bn by 2021 unless "radical joint action" is taken, it concludes.
Chair of EEDA Richard Ellis said: "We now have the economic evidence to support the East of England's case for continued investment in the transport infrastructure.
"The study is important not just in the region but nationally as well because the East of England is one of only three regional net contributors to UK plc. Maintained investment the region's transport network is therefore vital to the national economy and to help businesses compete in a global marketplace.
"Investment in transport is critical to supporting the regional and national economy but equally working smarter and managing demand will be key to unlocking economic growth.
"It now time for all of us to get behind our regional Transport Campaign to lobby for a more reliable, effective and safer transport network for benefit of all that live, work and invest in the East of England."
The research, conducted by Steer Davies Gleave concludes that:
Congestion in the East of England region is set to double to more than £2bn per annum by 2021, with £1.3bn as direct costs to business productivity.
Hotspots cause the most damage to the regional and national economy – 85% of the costs of congestion are borne in the region's seven 'engines of growth' (Thames Gateway and South Essex, Greater Cambridge, Greater Peterborough, Milton Keynes South Midlands, London Arc, Greater Norwich, and Haven Gateway).
There will be significant economic benefits from targeted road capacity improvements, but the economic returns from this approach diminish once the key constraints on economic productivity have been relieved.
New road infrastructure alone is not enough. Measures to manage demand for travel by road and investment in additional rail capacity will increasingly do more to reduce the cost of congestion in the long term. For example, through exploring various forms of demand management, traffic management measures like motorway hard shoulder running and longer trains.
Minister for the East of England, Barbara Follett said: "We are determined to get the best from our road network so that motorists in our region have reliable journey times on roads that are safe and well-managed. Congestion is frustrating and has serious consequences for the economy and the environment.
"I welcome the contributions to this workshop today. In our region we need to develop and implement more innovative approaches to the way we use our major roads. This includes measures like opening the hard shoulder when traffic is at its heaviest, alongside some conventional widening where that makes best sense.
"In July, Ruth Kelly, Secretary of State for Transport confirmed that work on the A14 Ellington to Fen Ditton widening scheme will start in 2010, and funding for improvements to the M25 Junction 30 near Lakeside shopping centre and a new A421 dual carriageway linking Bedford to the M1.
"We need to be smart about new investment in our infrastructure and I look forward to passing on some good ideas and suggestions that arise from our work here today,” she said.