Western Link for Norwich to cost £274m and will not open until 2029
The cost of a new link road in Norfolk has risen by more than £20m and it will open three years late.
The Western Link around Norwich has been labelled a "disastrous white elephant" by opposition parties, with calls for it to be scrapped.
Norfolk County Council blamed the increase from £251m to £273.9m on extra construction costs and delays due to uncertainty about Government funding.
But it insisted the 3.9-mile (6.3km) road represented value for money.
The Western Link Road would form a new ring road around the city, connecting the Broadland Northway - known as the Norwich Distributor Road - at the A1067 with the A47 at Easton
The council has argued it was needed to tackle congestion in the city to stop drivers using nearby villages as rat runs.
But environmental groups say it will go through woodland which is home to an endangered colony of bats and Labour councillors have said the project is "doomed".
The Department for Transport has approved the scheme and the Conservative-run county council revealed it will formally put in a planning application in early 2024, with preparatory building work starting at the end of 2025.
Construction will begin in the summer of 2026 and the road should open in 2029.
Graham Plant, the cabinet member for travel, transport and infrastructure, said the road was still "absolutely worth it" and suggested it would give a return of £2 for every £1 invested.
"It's crucial that we continue to invest in Norfolk's transport infrastructure to tackle existing traffic problems, support local businesses and enable our road networks to cope with planned housing and job growth" he said.
He added the Government, which has already committed £213m to the project, had indicated it may give up to another £38m towards the cost.
Mr Plant said if more Government funding does not become available, he would be pushing the council to provide the extra money.
Jamie Osborn, Green spokesman at the council, said the investment should instead be spent on improving public transport.
"This is a disastrous white elephant and should be stopped before any more money is wasted," he said.
Emma Corlett, the deputy leader of the Labour group, called the road to be scrapped.
"At the best of times this would be reckless and irresponsible but in the middle of the current cost of living crisis it beggars belief," she said.
The full council will discuss the proposal in December.
A spokesman for the Department for Transport said there would be discussions with Norfolk County Council about the details of any "uplift" of Government funding for the Norwich Western Link.
He said the details of the scheme were "still being considered" and would be subjected to the "usual assessment and approval process" .
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