Opposition councillors have criticised the ballooning costs of the Norwich Western Link road, calling the project the "wrong policy for the wrong time".
On Friday, Norfolk County Council revealed the cost of the 3.9 mile route - which stretches from the A1067 Fakenham Road to the A47 at Honingham - had spiralled to £251m, or £64m a mile.
Campaigners against the route said the increase means it is now time for the council to cut its losses and scrap the plan.
However, Norfolk’s Chamber of Commerce has reiterated its support, saying the route will help businesses.
Steve Morphew, the leader of the council's Labour group, said: "The numbers are eye-watering, and the affordability is more questionable than it has ever been. I'm still not convinced this resolves the environmental issues and habitat disasters for the bats.
"This is the wrong policy at the wrong time and will create more problems than it solves."
Jamie Osborn, a Green councillor, said: "They are pumping more and more money into this road and it is not clear what we are getting from it.
"At some stage, the council has to realise that spending £251m on a 3.9 mile road is not a good use of public money. There are other things the council should be prioritising than this destructive project."
The scheme has previously caused a split within the Liberal Democrat group, with Brian Watkins objecting to the project while much of his party is in support.
Mr Watkins said: "Whatever side of the argument you are on there is now real concern that this road is in danger of never being completed despite the millions of pounds that the Conservatives have already spent on it.”
He called for a "Plan B" to make sure the communities “blighted” by heavy traffic can be supported, fearing the project could bankrupt the council due to the high levels of borrowing needed.
Borrowing is expected to be around £29m.
However, Nova Fairbank, chief operating officer at Norfolk Chamber of commerce, said it was essential the road was completed as soon as possible.
“The overall cost of doing business is rising across the board and the announcement of increased costs for this vital piece of highway demonstrates the ongoing need to move our infrastructure projects forward as quickly as possible to avoid further delay and more costs," she added.
She said the road would support key industries, including agriculture, tourism and manufacturing by reducing journey times and opening new markets.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here