Critics of the Norwich Western Link have pledged to keep fighting the "disastrous" scheme - but supporters have hailed the government's decision to pump more than £210m into the controversial project.
The divisive 3.9-mile road, which would connect the Northern Distributor Road to the A47, west of Norwich, has had its outline business case approved by ministers.
The government will give Conservative-controlled County Hall £213m towards the cost of the road, with the bill estimated at £251m in summer 2022.
The road must still secure planning permission and other legal negotiations need to be concluded before the money will be released.
But supporters welcomed the announcement as a boost for Norfolk's economy and a solution to rat-running in areas around that side of Norwich.
Jerome Mayhew, Conservative MP for Broadland, said: "This investment of government funds is as much a vote of confidence in the commercial future of Norfolk as it is a support for today's communities."
Norwich North MP Chloe Smith said: "Having already helped to secure the investment that built the NDR, I support the Norwich Western Link because we must eliminate the 'rat-running' that disrupts residents in the northwest of the city and upgrade connectivity between Norfolk and the eastern region to incentivise investment."
Conservative county councillor Bill Borrett, who represents Elmham and Mattishall, said: "The villages that I represent, in particular Hockering and Lyng, have been blighted by traffic rat-running between the A1067 and the A47.
"It will make the rural lanes so much safer for all those that live in the villages west of Norwich."
Sharon Blundell, Liberal Democrat county councillor for Costessey, said: "I appreciate that not everyone supports the Norwich Western Link, but we have to think about villages which have roads that are not suitable for the amount of traffic that uses them.
"So this is good news for them, I realise that it will not magically make cars vanish from the roads, but it will keep the amount of traffic lower than if we did nothing.”
But critics, who said the road's price tag is now likely to be closer to £400m, pledged to keep fighting the scheme.
Norwich South Labour MP Clive Lewis said: "Today's announcement is disappointing, but it's not game over.
"The scheme has got to get through planning and I know many compelling reasons to turn down permission.
"The fight for environmental justice continues and I'll do whatever I can to stop this road."
READ MORE: Norfolk Wildlife Trust in bat plea over Norwich Western Link
David Pett, from the Stop The Wensum Link campaign group, said: "In the face of staggering environmental and financial costs, we question the council's decision to pursue the project.
"We fear this will lead to unnecessary borrowing and dipping into reserves which could be better utilised elsewhere, and which we know the council cannot afford.
"This road would come at a devastating environmental cost, altering habitats and potentially threatening local wildlife, such as the super-colony of bats that have already been affected.
"The approval process is far from over and we shall continue to oppose this project at every stage as we believe it poses significant risks, both financially and environmentally."
Eliot Lyne, chief executive of Norfolk Wildlife Trust, said: “Today’s decision is terrible news for Norfolk’s wildlife.
“In addition to the destruction of a well-connected network of vital wildlife habitats including ancient woods and trees, grasslands, chalk streams and floodplain, there is mounting and detailed long-term scientific evidence that the road will irreparably harm the UK’s largest population of rare and legally protected barbastelle bats."
He said huge sums of money were likely to be wasted on a project "not likely to ever obtain planning consent".
Emma Corlett, deputy leader of the opposition Labour group at the county council, said: "This is far from a done deal and feels like a gimmick, pre-general election.
"There's no chance of planning permission being given before an election and we know inflation will have pushed costs way beyond those figures.
"Far better to spend money on making our existing roads fit for purpose and starting on a properly integrated public transport service".
And Jamie Osborn, Green county councillor, said: "With the final price tag for the Western Link likely to be as high as £400m - over £100m per mile - there are still huge gaps in the funding.
"Continuing with the Western Link with that uncertainty would be disastrous for taxpayers as well as for Norfolk's environment."
Brian Watikins, leader of the Lib Dem group at County Hall said the cost of the road was likely to be higher than the £251m estimate, so there remained "important unanswered questions" about how the council would fund it.
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