The latest estimated cost of the Norwich Western Link is still not being revealed - prompting opposition councillors to blast the secrecy around the potential bill.
Norfolk County Council is still waiting for the government to confirm whether or not it will back the business case for the controversial 3.9-mile road and contribute 85pc towards it.
But opposition councillors at County Hall are frustrated the council is still not revealing the latest estimate for the cost of the road, to connect the Norwich Northern Distributor Road to the A47 west of Norwich.
The last £251m estimate was given more than a year ago and critics claim the bill is now likely to be closer to £400m.
There is no update in next month's agenda of the Conservative-controlled council's cabinet and leaders say it will be November before another update is provided.
Emma Corlett, deputy leader of the council's opposition Labour group, which wants the road scrapped, said: "I think the public and all 84 councillors have a right to know how much this scheme is now estimated to cost."
The council has already spent close to £40m on the scheme, including through money borrowed and from the council's reserves.
Ms Corlett warned: "If the council borrows money it will cost more at the moment and, by using money from reserves, it means they miss out on the higher interest rates that money would accrue - which could be used to help under-pressure services like adult social care."
The council's cabinet agreed in July to scale back development work, due to the lack of a decision from the government.
Graham Plant, cabinet member for highways, infrastructure and transport at Norfolk County Council, said: "The situation remains unchanged since that meeting.
"We want to get on with delivering this important infrastructure project for Norfolk, which will significantly reduce traffic congestion, shorten journey times and improve road safety.
"We’re continuing to push for a decision and intend to bring a report to the November meeting of cabinet to provide a further update and agree next steps."
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