The 'agonisingly slow' progress to get £300m of promised work started on the A47 has prompted angry council bosses to call for a watchdog to take action.
In 2014, the government announced millions of pounds was available for work on sections of the road.
That includes stretches between North Burlingham and Blofield, from Easton to North Tuddenham, at Thickthorn and at Great Yarmouth.
The work was meant to happen between 2015 and 2020, but no construction has taken place.
And a report by officers at Norfolk County Council has called on traffic regulator the Office of Rail and Road (ORR) that it should hold Highways England - the agency tasked with doing the work - to account.
Officers, who are concerned the revised dates of 2021/22 for work to start will not be met, have produced a hard-hitting report for the regulator.
In it, they state: "This is a major area of concern for the county council.
"The expectation when the government announced the inclusion of the A47 schemes within the programme for 2015-2020 was that they would be constructed within that period.
"We have, however, yet to see a start on any of the schemes."
The report adds there has been "constant churn" in who represents Highways England and their consultants and bemoans a "lack of knowledge" about Norfolk "due to the geographical remoteness of Highways England" from the county.
It adds: "Progress in development and delivery of the schemes has been agonisingly slow. Norfolk is extremely concerned about the ability of Highways England to deliver such projects."
County Hall's submission to the ORR, which is in response to consultation with public bodies on how it holds Highways England to account, calls on the regulator to "meaningfully intervene" at an early stage.
Martin Wilby, the council's cabinet member for highways and infrastructure, said: "Norfolk is missing out on economic growth, new homes and jobs because of this continued delay.
"It's unacceptable and we want the regulator to intervene early in cases like this."
A Highways England spokesperson said: "Taken separately or together, Highways England's £300m portfolio of upgrades for the A47 will deliver real benefits for the thousands of people who depend on it every day. We share the Norfolk County Council's eagerness so see the upgrades delivered as soon as possible and value their support as we take each scheme through its development."
The Eastern Daily Press has, along with Norfolk County Council and the Norfolk Chamber Of Commerce, been calling for the government to commit to full dualling of the A47.
A delegation from Norfolk headed to Westminster last year to make the case for the Just Dual It! campaign.
MORE: Norfolk has lost money due to A47 work delays, claims angry councillor
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