And because the NBN was being built to become the monopoly wholesale broadband provider in Australia, it was 'an affront' to the nation's competition laws.
"The Government has not even asked the question of whether there is a cheaper more cost-effective way of providing better broadband to all Australians," Mr Turnbull told press at Parliament House.
"They declined to have McKinsey ask that question, so there's been no cost-benefit analysis done. The reality is this is a gigantic leap in the dark."
Mr Turnbull said the NBN was being constructed as a Government owned telecoms monopoly and was "so much of an affront to our competition laws '¦ that it could never get approved by the ACCC."
"So the Government has to pass special legislation, if they can get parliament to do it, to take the NBN out of the provisions of the Trade Practices Act," he said.
Mr Turnbull contends that the mathematics of the $43 billion NBN and the roughly nine million households put the cost of its construction at about $5,000 per home.
But Communications Minister Stephen Conroy said the numbers were false and that Government was expecting to soon receive details on how many homes and businesses were to be connected to the fibre network and a timetable of when and where the roll-out would start on the mainland. He has committed to making that information publicly available.
"We are about to receive in the next few weeks that sort of information from (NBN Company) and I am sure there is a whole range of information that we will be making available very, very shortly on some of these key questions," Senator Conroy said on ABC television's Lateline.
"We will be very, very happy to put it out in to the public domain," he said.