NBN chief Bill Morrow signalled the broadband network will announce a new pricing deal by Christmas that will offer Australians faster speeds at more competitive prices.

As the government-owned network has come under increased scrutiny over both the roll out of the network and advertised speeds not being delivered, Mr Morrow fronted Senate estimates on Tuesday evening to face questions from Labor, government and cross bench senators.

The chief executive faced a barrage of questions over the threat posed by the looming roll out of 5G fast mobile broadband, a so-called digital divide that critics argue is developing between people who have fibre to the home and the slower fibre to the kerb option, and about the current pricing review under way.

Prime Minister Malcolm Turnbull said on Monday the project may have been a "mistake" - at least as envisaged by the former Labor government - and admitted there were questions over whether the giant infrastructure project would ever make back the money invested by taxpayers.