Labour leaders at Norwich City Council have reiterated their support for the Western Link, despite party colleague Clive Lewis warning 'future generations will mock the names that are attached to it'.
Norfolk County Council recently announced its preferred route for the £153m road, to connect the A47 to the Norwich Northern Distributor Road.
The route would go halfway between Weston Longville and Ringland and include a 720m long viaduct to take it over the Wensum Valley.
Norwich South MP Mr Lewis has warned it would "be a monument to the folly of politicians who never got the memo about climate change and ecological destruction".
But the Labour-controlled city council cabinet previously said it would support the road, so long as it comes with sustainable transport measures for Norwich.
At a City Hall meeting tonight, opposition Green Party leader Denise Carlo challenged the Labour cabinet to reconsider its support in the light of their colleague's remarks.
She said traffic would increase carbon emission by 19.5pc between 2025 and 2040 and it would disturb maternity roosts of Barbastelle bats.
Mike Stonard, cabinet member for sustainable and inclusive growth, said he was aware of the opposition from Mr Lewis, but added: "The south of the city has, for many years, benefited from the southern bypass, which has removed traffic from his constituency.
"The city council has a duty on behalf of the whole city - north as well as south.
The Western Link will deliver benefits for everyone, but especially those who live in the north and west of the city, an area which still experiences traffic similar to that in the south before the southern bypass was built."
Mr Stonard said the cabinet's backing was not the council's final decision and said it hinged on transport investment and mitigation.
He said "a lot" of the claims about the impact on the environment and climate change were "based upon conjecture" and wanted to wait until full analysis and modelling.
He said: "If at that stage, the planned mitigation measures do not offset the potential environmental harm of the road, then will be the time for the city council to reconsider its support."
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