A wildlife trust says it has 'grave concerns' over the impact of the mooted Western Link on important habitats and vulnerable species.
The chief executive of Norfolk Wildlife Trust says the £153m road would destroy parts of three County Wildlife sites and is not convinced by the council's claims it will leave wildlife in a better state than before construction.
Norfolk County Council's Conservative-controlled cabinet this week agreed to Option C as their favoured route for the road.
It would be a 3.9-mile road from the A1067, near the NDR, travelling halfway between Weston Longville and Ringland, and linking to the A47 at a new junction at Wood Lane near Honingham. It would require a 720-metre-long viaduct over the River Wensum.
But Norfolk Wildlife Trust said it would affect County Wildlife sites at Primrose Grove, Foxburrow Plantation and the River Wensum Pastures.
Pamela Abbott, the trust's chief executive, said: "The decision presupposes there is no realistic alternative to the road link, although we and others believe that case has yet to be fully made.
"The core route of this road, even without considering all the additional infrastructure, would destroy parts of three County Wildlife Sites and permanently sever important connections between remnant parts of important habitats and populations of vulnerable species for nearly four miles.
Whilst we recognise and endorse the council's aspiration to deliver a net gain for wildlife alongside this scheme, we have grave concerns about how this will be met, and whether appropriate measures have been included in the budget."
Martin Wilby, cabinet member for highways, infrastructure and transport at Norfolk County Council, said the council had analysed whether encouraging people to walk, cycle and use public transport alone would address traffic congestion and rat-running and concluded it would not.
He said the road had strong support, including from businesses. And he said 86pc of people who responded to consultation last summer saying they wanted a new road.
He said: "We know there are concerns about the Norwich Western Link's impact on wildlife in the area and I'd like to assure people this is something we're taking very seriously.
The project's budget of £153m does include estimated costs for measures which will help us achieve biodiversity net gain. Our ecologists working on the project have had discussions with Natural England about our approach to create and restore habitats and as a result we're likely to focus on creating woodland and wetland habitats.
"We're very keen to work with Norfolk Wildlife Trust and other similar organisations, which is why we've set up our Norwich Western Link Ecology Liaison Group to share information and ideas and provide in-depth local insight on ecological matters."
MORE: Western Link from NDR to A47 would destroy habitats, say owners of woodland
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