Campaigners made a complaint to the Local Government Ombudsman after Crow Lane remained controversially blocked to traffic for 17 days.
It had been expected to reopen on December 1 when temporary permission to close it under emergency Covid-19 legislation ran out.
Residents said the continued closure after December 1 was ‘unlawful’.
Derbyshire County Council confirmed it was aware a complaint had been submitted to the ombudsman.
In a letter to the resident who made the complaint, seen by the Derbyshire Times, Claire Mead, an investigator for the Local Government and Social Care Ombudsman, said: “I have assessed your complaint to see whether we can and should investigate it.
"I have decided we should consider it further and have passed it to our investigation team.”
She admitted it ‘may be some time before our Investigation team is able to start looking at your complaint’.
Philip Riden, chair of Chesterfield and District Civic Society, who has played a leading role in a campaign to reopen the road, also threatened to write to the government about the closure.
In a letter to County Hall he said: “As far as I can judge, the continued closure of this section of Crow Lane to motor traffic is an unlawful act by the county council.”
A spokesperson for Derbyshire County Council said: “We are aware that a complaint has been submitted to the Local Government Ombudsman, however Crow Lane re-opened to all traffic on Friday 17 December.”
The council has made no secret of its long term plan to close Crow Lane to traffic so it can become part of a new east-to-west cycle path across Chesterfield.
"It is our intention to carry out the necessary process to make this closure permanent, and while we carry that out we will be looking to safely re-open the road to traffic,” a spokesperson said earlier this month.
The long-term closure has proved unpopular with some residents in the area and 2,000 people signed a petition demanding it was reopened.
They said Crow Lane was well used as a through route and its closure would increase congestion on other roads.