Cheaper data and the roll-out of 5G technology could be a viable competitor to the NBN.
Mobile prices fell 17 percent in 2019-20 thanks to a drop in the cost of entry level plans and significant growth in data allowances, according to the ACCC's annual Communications Market Report.
The consumer watchdog noted a modest 2 percent fall in NBN broadband prices with an increase in the cost of entry level plans tempering the decline.
"The growth in data allowances for mobile services means consumers received better value from their mobile plans," chair Rod Sims said.
"Whether this trend continues into 2021 will depend on how strongly mobile operators compete for new customers."
The ACCC noted that while the 5G footprint is limited, operators continue to invest in roll-out plans to bring faster speeds, lower latency and the prospect of greater competition with fixed line broadband services.
"The impact in the mobile market is likely to depend on the willingness of consumers and businesses to upgrade to more expensive devices," Mr Simms said.
According to comparative website WhistleOut, 5G speeds for home internet vary between around 50Mbps and 300Mbps.
In terms of pricing, Optus offer a $75 per month plan capped at 100Mbps which WhistleOut says is cheaper than most NBN 100 Mbps plans.
It also offers a $90 option with uncapped speed and both plans have unlimited data.
Telstra charge $85 per month for a 500GB plan currently available on an invite-only basis.
"From my perspective, 5G is far more interesting as an NBN alternative than it is for mobile devices right now," WhistleOut Managing Editor Alex Choros said.
"Given the speeds you can achieve for prices similar to NBN 50 and NBN 100 plans, it will be a compelling option for many Australians, especially those struggling with subpar speeds on Fibre to the Node connections or Fixed Wireless.
"As the 5G rollout progresses, it's inevitable NBN Co and NBN providers will have to factor this into how plans are priced."
In September NBN Co announced it had concluded its initial build and the ACCC said this underlined the importance of commercial access arrangements to encourage competition in retail markets.
"There are promising signs of further consumer benefit as RSPs (retail service providers) take up improved offers strengthened via commercial negotiation undertaken over the course of our public inquiries," Mr Sims said.
"The importance of maximising use of the NBN through improved affordability and strong retail competition cannot be overstated if we are to realise the full economic and social benefits of this significant investment."
Australian Associated Press