Norwich City Council's "in principle" support for the £153m Western Link Road has been withdrawn unless conditions are met.
The Labour-run council made the announcement during a question from Lucy Galvin, a member of the public, at a cabinet meeting.
In a statement, councillor Mike Stonard, cabinet member for sustainable and inclusive growth, described the scheme as a "major and controversial proposal".
He said: "If built, it will have significant implications for Norfolk’s carbon emissions, its environment, traffic conditions across the city and economic activity in the north of the city."
Councillor Stonard stressed plans for the construction rest entirely with Norfolk County Council and the city council's support was dependent on conditions being met.
In particular, the city council is calling for an "environmentally progressive strategy" for transport development in Norwich, which would see public transport and cycling promoted over car use.
He added: "We have as yet received no evidence that traffic levels in the city’s streets will be eased in a way that would improve air quality or enable modal shift or road space reallocation as a result of the construction of the NWL."
In his conclusion, he said: "If the Tories at county want us to change they’ll need to answer the questions, provide the evidence, reinstate the Highways Agency, or something very much like it, deliver on our bold Transport Plan and give us a meaningful say in transport and highways matters in the city.
"Until then, just as before, we cannot consider support."
The development of the link road, to connect the Broadland Northway, formerly the Northern Distributor Road (NDR), from the A1067 to the A47 west of Norwich, is one of the county council's top infrastructure priorities, but has already met with much opposition.
The Green Party and a local campaign group said they were pleased to see the council withdraw support, calling on the county council to halt the plans.
David Pett, from the Stop The Wensum Link campaign group, said: "The time is right for a pause and review of transport in and around Norwich, and for local councils to develop a sustainable transport system fit for the post-COVID world."
Councillor Jamie Osborn said he and his Green Party colleagues had consistently opposed the constructions, stating "building new roads is not a solution to better transport."
In response to the announcement, Norfolk County Council has insisted that the NWL will take traffic out of the city and bring associated benefits for Norwich.
Cllr Martin Wilby, cabinet member for highways and infrastructure at Norfolk County Council, said: “It’s clear that the city council sees the potential value it can create for Norwich and we absolutely will be looking to maximise these benefits as part of our Transport for Norwich strategy.
"We’ll continue to discuss this with our colleagues at the city council.”
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