There are could be as many as 3,500 unadopted roads in Northern Ireland and 1,200 sewerage schemes in backlog, the Regional Development Committee deputy chairman said, on 4 December 2012.
Sean Lynch of Sinn Fein gave the figures as he presented the committee's report into unadopted roads in Northern Ireland to the Assembly.
He said committee members were advised the number could be anywhere between 1,200- 3,500, although the Department for Regional Development and NI Water were unable to quantify how many there were exactly.
Mr Lynch said this was viewed as a "significant weakness" and the report had made recommendations to address the matter.
The Fermanagh and South Tyrone MLA said the committee was told it would cost an estimated £300m to bring roads up to a sufficient standard, and significantly more for improving waste water schemes.
"It is extremely unlikely that these levels of investment can be found from central government," he said.
He added that the committee had heard some "horrific stories" of residents of unfinished housing developments being left liable for thousands of pounds because roads and sewers were unfinished and unadopted.
Mr Lynch said the report was not intended as a criticism of contractors, but was aimed at ensuring greater protection for consumers.
The motion, tabled by the committee, sought approval for the report's recommendations and called on Regional Development Minister Danny Kennedy to implement them in conjunction with his Executive colleagues.
The second part of the debate can be viewed