Fresh plans were revealed for the four-mile stretch of road this week by Shropshire Council, which claim to cut the cost by £7 million and slash the carbon impact by 22,000 tonnes.
However Better Shrewsbury Transport say they are "disappointed" with the revised plans for the road, which would run from Churncote Island to Battlefield.
Dave Green, spokesman for the campaign group, said: "From statements made by Highways portfolio holder, Councillor Steve Charmley, a few weeks ago, we were expecting major changes to the scheme.
"However, it seems that the revised plans are nothing more than green wash. From our first look at them, they look like a pretty cynical attempt to sidestep residents’ concerns over the environmental and financial costs of this disastrous road."
The council’s amendments to the controversial road focus on changes to the bridge across the River Severn, reducing the lanes from three to two and removing a ‘crawler lane’ for HGVs, while shortening the length.
Mr Green added: "These revisions cannot change the fact that the road is fundamentally damaging to the environment. Even with the changes, the road will emit loads more carbon than it could possibly save during its lifetime.
"We also note that in the small print of their announcement they admit that the £80 million figure is based on their 2017 costs for the road which, only last month we showed to be hopelessly optimistic by comparison to the published prices of other recent, comparable projects like the Congleton Link Road in Cheshire. After the Shrewsbury shopping centre debacle, we do not have any faith in the council’s ability to budget for this multi-million pound scheme properly, particularly not at the time when the council is teetering on the brink of bankruptcy.
"If Councillor Charmley is convinced by the figures, will he personally guarantee that there will be no overspend?
"We have serious concerns that the new plans for the scheme will inevitably increase the risk of flood upstream as the viaduct has been partially replaced with an embankment in the flood plain. Apparently the council hasn’t learned anything from its own climate emergency strategy, which highlights the increased risk of flooding in the county over the coming years."
The campaigners say they will continue examining more than 100 revised documents and issue a more detailed rebuttal in due course.
In the meantime, though, the group is calling on the council to clarify the objection process.
Mr Green said: "The council has yet to explain how this next round of objections will be handled or what the time frame is for them. We hope that the council will be contacting the 4,000 plus objectors to the original scheme directly and will invite them to comment on the new proposals. We also hope that sufficient time will be given to the public to read and digest the raft of new documents. We remain convinced that this road is a disaster for the county and should be cancelled immediately."