The Campaign For Better Transport named the route as one of four in the country which had failed to deliver on a promise to ease congestion.
It accused the Highways Agency of underestimating future traffic levels and the impact of air quality, noise and greenhouse gas emissions when looking at road improvements.
The group studied a number of the Highways Agency's own evaluations of road schemes.
It said its findings cast 'major doubts on the value for money of road building'.
Derrick Coffee, East Sussex representative for the Campaign for Better Transport, said, "The Polegate Bypass has had a temporary and limited number of positive effects locally, but the overall picture is one of greatly increased traffic levels, less use of public transport, and a general inertia across the whole range of non-car alternatives.
"Even the few positive effects – less traffic on the old A27 and A22 – are limited, and from day one, the traffic levels have grown, eating away at those benefits."
Mr Coffee said there had been a 32 per cent increase in traffic and no reduction in journey times.
But the Highways Agency disputed this and said journey times on the Polegate bypass were half that of the B2247 (Dittons Road, Station Road and Hailsham Road) which runs through Polegate.
It also said it had improved safety and reduced traffic levels on roads around the area.
A spokesperson said, "We are committed to tackling congestion and providing a safe, reliable and sustainable road network that delivers value for money.
"The schemes focused on by Campaign for Better Transport do provide value for money and have improved safety, reduced congestion and made journey times more reliable for road users - as well as improving the local environment for many residents.
"To ensure decisions are made using the most robust information, we use the latest data and traffic modelling methods available to us.
"However we are not complacent and we are constantly working to improve our assessment of all the aspects that feed into scheme appraisals.
"We will continue to progress the up to £6 billion national roads programme – as outlined by the Government in January 2009 – bringing vital and much needed improvements to the national road network."