In a statement on Monday, NBN Co's chief network engineering office Peter Ryan said in the case of about half the premises ordering an HFC service, the company's technical staff needed to visit said premises and build a new lead-in conduit to connect the co-axial cable into the premises.
This was "something that can often be problematic and can cause delays", he admitted.
Given this, Ryan said it had decided "to hold back a proportion of these premises in order to better manage consumer expectations on wait times once they've placed an order".
Reacting to this, Labor shadow communications spokesman Michelle Rowland described the situation as a multi-technology mess.
"It’s remarkable that we are approaching 2018, and the company is conceding the HFC rollout still has them in knots," she said. "In orchestrating the 2013 NBN Strategic Review, Malcolm Turnbull thought he would roll out of bed one morning and switch on the HFC network like it was a toaster.
"The Strategic Review indicated 2.6 million premises would have access NBN over HFC by the end of 2016. Yet by the end of 2016, the NBN half-year report indicated only 159,000 premises could access the NBN over HFC."
Laurie Patton, the executive director of Internet Australia, a body representing Internet users, said first the NBN Co had been forced to abandon the use of the Optus HFC network because it was not fit for service and now expenditure was needed on the Telstra HFC network too.
A constant critic of the current rollout plan, Patton said the latest issue reinforced the need for a bipartisan rethink and an agreed strategy for a 21st century NBN.
"The way we're heading now, whoever is in office in 2020 will have to deal with our biggest ever national infrastructure debacle," he said.
"NBN Co will owe the government circa $19 billion and within 5 to 10 years it will need to fund a very expensive FttN replacement. So far no-one seems have even started working out how many billions this will cost."