In a doorstop interview, Turnbull said claims by the Prime Minister, Julia Gillard, and communications minister, Stephen Conroy, that a cost-benefit analysis would simply were false.
"This is one of the great furphies that Stephen Conroy has put up as a reason for not having a Productivity Commission inquiry," Turnbull said. "A Productivity Commission inquiry could be completed within six months, so say by the end of May next year.
"It would be very able to do that work. It would not put a brake on any of the experimental demonstration sites that are being rolled out at all."
Turnbull also claimed that recent suggested any delay to the NBN's rollout, should it occur, could be beneficial.
"And indeed, one of the other recommendations of the OECD that has not had a lot of coverage to date is that they actually recommended a more prudent, slower, roll-out of the NBN so that you could actually see what the take-up is and what the experience is in the take-up sites," Turnbull said. "But the [Productivity Commission] inquiry would not have any impact on the roll-out at all."