Labor has played down expectations of a rapid and major overhaul of the National Broadband Network if it wins government, ruling out a "quick fix" and instead promising a responsible approach to the vexed $50 billion project.

In a speech on Thursday, Labor communications spokeswoman Michelle Rowland said the Coalition's approach had simultaneously driven up the costs of the project and damaged its revenue potential, arguing her opponents did not anticipate how complex the NBN was before coming into government in 2013.

Labor's communications spokeswoman Michelle Rowland. Credit:Fairfax Media

She said the many layers of the massive project meant it would have been "near impossible for any opposition party to grasp what they were tinkering with".

"The irony of this situation is that the Liberal Party promised its multi-technology mix would be faster and cheaper, yet we now have a business model that is in more need of cash flows — but has less capacity to generate it because of inferior technology and higher costs," Ms Rowland told the Sydney Institute.