Broadband modems supplied by Australian internet retailers are incapable of delivering 100 Mbps download speeds over the average fibre-to-the-node connection, according to the consumer watchdog's own performance testing.

At the same time, poor Wi-Fi performance from supplied modem/routers is another key bottleneck stopping Australians enjoying their promised NBN speeds.

Testing of 43 modem/routers from 11 different hardware makers and 10 internet providers, found that none could achieve 100/40 Mbps broadband speeds over a 450-metre copper run, which is the average length of copper in an NBN FTTN connection.

Customers may not be able to achieve the speeds they pay for.

At this distance from the node, download speeds vary from 60 to 94 Mbps and upload speeds from 10 to 29 Mbps, according to an independent modem/router performance testing report commissioned by the Australian Communications and Media Authority.