Rows of chairs were full and several people had to stand at the Bicton Village Hall event as representatives from various groups spoke against the major transport project.
The scheme to link up Shrewsbury's Battlefield Link Road and the planned Oxon Link Road with a new road and relieve traffic in the town has been mooted for decades, but recently secured financial backing from the Government.
It will include a new bridge over the River Severn and its flood plain, and a new bridge over the Shrewsbury-Chester railway line.
Dave Green from Friends of the Earth Shrewsbury told the 90 or so attendees at Bicton that the cost of building the road, now estimated to be £71m, could easily rise because the proposed route will go through land that "has never been built on".
In March last year the Department for Transport awarded £54m to the project, but Shropshire Council will provide the balance and will also be responsible for any cost increases.
Mr Green also expressed doubt that the new road would reduce traffic time in the town and said it would actually lead to more people using the minor roads that link to it.
"I do not believe you need the road for growth," he said.
Robin Mager from the Shropshire Wildlife Trust said that within 500m of where the road is due to be built, hundreds of animal species including bats, otters, birds and hedgehogs have been recorded.
He cited Rob McBride of the TREEspect Community Interest Company, who said that there were "ancient, veteran and notable trees" in the area that will be affected.
Peter Gilbert from Sustainable Transport Shropshire pointed to the Welsh Government's decision last year to scrap the proposed M4 relief road, partly attributed to the climate emergency, as an example to follow.
"Where Wales leads, Shropshire needs to follow," he said.
He also said that road space in the town should be used "more efficiently" and the council should encourage more sustainable methods of transport than travelling by car.
He urged the audience to use their "people power" and make their thoughts clear to councillors.
Emma Bullard of the Green Party said she previously worked at Shropshire Council's planning department, and that building new roads is not the best way to reduce congestion.