NBN Co will need to improve dramatically the speed at which it rolls out its fibre-optic network to meet the connection targets it set only last year.
Only 72,400 premises had been passed by the end of December after 18 months of fibre roll-out, according to figures it released on Monday. This means that, to meet its own targets, NBN Co needs to pass another 268,000 premises in the next five months.
The company's aim is to pass 341,000 new and existing premises with fibre-optic cable by June.
The chief executive, Mike Quigley, vowed to improve the speed of the the roll-out in the second quarter of the year.
He said the slow connection rate was a reflection of progress in "the early stages of the rollout" and he blamed delays on difficulties in sorting out contractual agreements that it must sign with companies such as Telstra.
He promised a rapid acceleration in the rollout during the second quarter of the year.
"The rollout is not a linear progression, but a rapid ramp-up. We are targeting to pass more premises in the final quarter of the financial year than we will have passed in the entire project up to the beginning of that quarter," he said.
"Additional construction resources will be added over the coming months to help achieve these targets."
NBN Co defines passed premises as where cable has been laid in the street but houses are yet to be connected.
The company expects to pass more than 50,000 premises next month, according to its figures. It predicts a rapid acceleration of the roll-out, from close to 100,000 premises in March to about 150,000 in April.
In May, the company hopes to pass more than 200,000 premises, reaching its target in the final month of the financial year.
The opposition communications spokesperson, Malcolm Turnbull, was quick to dismiss NBN Co's definition of "premises completed or under construction".
"Construction begins according to the NBN Co without anyone even putting a crowbar into the ground. It begins 'when NBN Co issues contract instructions to its contractors for a Fibre Service Access Module'," he said on his website.