Almost a quarter of a million homes and businesses could be unable to reach the legally required minimum national broadband network speed.
An NBN Co report tabled in parliament two days before Christmas showed 98 per cent of all premises were able to hit the minimum legal requirements.
But that leaves two per cent or about 238,000 unable to meet the benchmark.
Telecommunications laws require all Australians to have access to minimum broadband speeds of 25 megabits a second.
The report argues the vast majority of the two per cent not able to reach 25 megabits a second are able to hit 20 megabits a second.
But Labor has pounced on the findings, arguing the research admits decaying copper lines are causing speeds to get worse.
Opposition Leader Anthony Albanese said the coalition's "dud" NBN was suffering from its decision to replace Labor's fibre-to-the-premises plan with a copper-based system.
"With many Australians still working from home while the COVID-19 pandemic continues, the Morrison government's failure to deliver a basic NBN service is a handbrake on Australia's economic recovery," he said.
On the same day the report was tabled in parliament, Communications Minister Paul Fletcher declared the NBN built and fully operational.
"The government also recognises that there is continuing work to enhance the capabilities of the network," he said.
The coalition last year announced a $4.5 billion upgrade to move six million home from copper to ultra-fast fibre connections by 2023.
After coming to power in 2013, the government announced a goal for every home and business to have download rates between 25 and 100 megabits a second by later 2016.
A 2016 statement of expectation directed NBN Co to provide broadband services with a minimum download data rate of 25 megabits.
Australian Associated Press