Major changes to the implementation of the national broadband network will be needed to avoid huge cost blow-outs and up to 300,000 homes missing out on high-speed internet, Communications Minister Malcolm Turnbull will warn in a speech on Wednesday.

Mr Turnbull will tell the CommsDay telecommunications conference in Sydney that the likely demand for broadband in the areas where it is most costly to deliver has been dramatically underestimated.

Communications Minister Malcolm Turnbull. Credit:Andy Zakeli

While most Australians will have access to fibre-to-the-home or fibre-to-the-node services, about 1 million households, most in regional areas, will depend on wireless and satellite services.

Mr Turnbull will announce that NBN Co’s latest modelling shows demand in non-fixed line areas has been underestimated by two to three times. This means there will be a take-up of up to 620,000 wireless and satellite connections instead of 230,000 connections.