Rowland told iTWire: "We recognise the challenging task that Morrow has grappled with in implementing the Turnbull Government's multi-technology mix."

Her reference was to the mix of technologies that the Coalition Government decided to adopt once it came to power in 2013.

The original Labor plan had called for 93% of premises to have fibre-to-the-home and the remaining 7% to be covered by fixed wireless and satellite, depending on the physical accessibility.

But the Coalition put fibre-to-the-node at the head of its technology list, with HFC just behind. Satellite and fixed wireless remained on the menu as well.

Rowland said: "But let's be frank about the issues – the long-term economics of the NBN are a mess. This sits squarely on Malcolm Turnbull. (The year) 2018 is an opportune time to exit."

Morrow had conducted himself as a professional and performed the role consistent with the policy direction of the Turnbull Government, she said.

"The predictable timing of this departure is no accident," Rowland said. "It highlights the problems Labor has consistently argued in relation to the long-term economics of Malcolm Turnbull’s flawed multi-technology mix.

"At the end of all this, Australia would have spent $50 billion on an inferior network that costs more and does less. No-one in their right mind would spend that amount of money on a network dominated by copper and HFC.

"There will come a point where tactical pricing discounts can no longer conceal the failures of this government."

Rowland said these "failures sit squarely on the shoulders of Malcolm Turnbull and his decision to abandon fibre".

"Irrespective of personnel changes at NBN, Turnbull’s flawed policy direction will continue to deliver poor outcomes for Australian consumers and businesses."

The Australian Greens digital issues spokesperson Senator Jordon Steele-John said Morrow's resignation was a thinly-veiled attempt to absolve himself of any responsibility for the mess it has become.

He said the service most Australians would be left with when Morrow vacates the position would not be the service that he, or the Turnbull Government, promised to deliver.

"Access to fast, secure and stable internet is a human right, and FttP technology is the only long-term solution to meet Australia's current and future broadband needs," Senator Steele-John said.

"Furthermore, the rollout of the NBN has suffered from a serious lack of honesty, transparency and accountability at all levels — government, NBN Co and retail providers — that must be addressed to restore public trust."

He said as chief executive, Morrow must share the burden of responsibility for the overwhelmingly negative experience, that connecting to the NBN had become for so many Australians, with Turnbull.

"We have an opportunity to build a high-speed, national system that would raise Australia's digital readiness and bring our speeds into line with world leaders such as South Korea and Japan," Steele-John added.

"But, in its current form, the NBN will never deliver the average 100Mbps speeds that have been promised by Morrow and the Turnbull Government."