Dark, unpaved streets across housing estates in Northern Ireland could cost up to £300 million to repair.
Around 1,200 public roads have been identified as inadequate, but there could be as many as 3,500, according to figures contained in a regional development committee report.
Many have not been levelled, paved, lit or provided with sewerage to the official standards because developers ran out of cash and could not afford to finish their projects.
A street in bad condition could drive down the resale value of local properties and it could take a further £41 million to £100 million to fix the 1,200 sewerage schemes that are currently backlogged, said the committee report.
Deputy chairman Sean Lynch said MLAs had heard "horror stories" from people living on ghost estates.
He said: "People were left in a huge mess, bin lorries couldn't get down the street, people were having to wheel their bins to the lorries because of the state of the roads. It's very dangerous to residents, particularly to families with young children. There was a case in the south where a child drowned in a hole that hadn't been filled."
The inquiry recommendations included amending Private Street legislation to ensure it can deal with the increasing occurrences of unadopted (unfinished) roads.
"The fact that DRD (the Department for Regional Development) are unable to even quantify the precise number and cost is disturbing and unacceptable," said the Sinn Fein MLA for Fermanagh South Tyrone.
The economic downturn means the number of unadopted roads is on the increase and Mr Lynch said resolving the issue would come at significant cost to the department and the executive. "We know that it's not going to happen overnight," he added.
Stewart Dickson, the Alliance Party's regional development spokesman, said the priority list is a sensible recommendation and the Assembly and Executive must help developers and buyers who have been affected by recession.