Council leaders are facing claims the authority could become bankrupt if the £274m Norwich Western Link scheme does not go ahead.
Opposition councillors have warned that the ruling Conservatives at County Hall have risked the financial future of the authority in their determination to get the proposed 3.9-mile road built.
They say that Norfolk County Council has now committed so much cash to the project that if it does not now go ahead, the authority would not be able to balance the books.
It comes at a time when a number of English councils have been forced to effectively declare themselves bankrupt, because of their financial dire straits.
Jamie Osborn, Green county councillor, said: "Proceeding any further with the Western Link would put the council at risk of bankruptcy."
He said that if the scheme were scrapped, the council would have to make cuts to services to stave off bankruptcy.
"Should the Western Link be cancelled for any reason, the cost incurred thus far will revert from capital to revenue and, in order to cover that cost, we'll have to ask all departments to make further cuts," he added.
But Conservative councillors hit back, insisting the risks around the road's funding had been taken into account and were manageable.
During a council debate about the controversial scheme just before Christmas, County Hall officers conceded they could not put a figure on how much the road's price tag would have to reach before a decision on whether to pull the plug could be needed.
The cost of the road has so far soared to £273.9m, from the £153m estimate when the route was picked in 2019.
There is still uncertainty as to how much the government will provide. The Department for Transport has agreed to give £213m, but the council says the door has been left open for it to get £251m, so discussions continue.
If it gets £251m, the council would have to contribute £23m drawn from borrowing and reserves.
But if it only gets £213m, just over £60m would have to be found by the authority which already needs to make £46m in savings and cuts to set a balanced budget next year.
In the debate, Mr Osborn warned if the road does not get built, the council, which has already spent at least £40m and got a further £26m from the government this month, could have to reimburse the Department for Transport.
Council documents reveal that if money does have to be paid back, then the council would have to get departments to make savings or raid reserves.
Mr Obsorn said factors outside the council's control could scupper the scheme, such as a legal challenge, failure to secure planning permission or further cost rises.
However, Graham Plant, the council's cabinet member for highways, infrastructure and transport, stood by County Hall's commitment to the road.
He said: "Securing the financial backing from the government is an endorsement of the Western Link, the county council and the county as a whole.
"If it wasn't given to Norfolk, this money would be spent elsewhere in the country on other projects."
He said it was "a good investment" and that he and Tory cabinet colleagues had considered the risks when deciding to keep pursuing the road.
He said a £70m 'risk element' had been factored in to the latest projections for the scheme and that any future changes in the cost would be reported to cabinet and full council.
READ MORE: Norwich Western Link supporters back new £274m Norfolk road
Green county councillor Paul Neale asked how much the road's bill would have to reach before it became unaffordable.
Harvey Bullen, the council's director of strategic finance, said: "It's a very simple question, but with a very complicated answer.
"It depends on a number of factors, which could change over time - if the cost screen were to increase, if the government choose to withdraw the funding for the schemes... quite frankly, we cannot really answer it, because there are several different answers to it."
He said it was ultimately a decision for the council's administration, which would have to find resources to pay for it, should it keep its commitment to the project.
The council is set to submit an application for the road, which would connect the Norwich Northern Distributor Road to the A47 west of Norwich, to its own planning committee next year.
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