NBN Co is unlikely to switch construction to a fibre-to-the-node model until late 2014 due to the complexity of changing the network architecture, the company’s executive chairman told a Senate estimates committee.

Getting every premises connected to speeds of at least 25 megabits per second [Mbps] by the end of 2016, as promised by the Coalition during the last election, was a "very, very tight timetable", Ziggy Switkowski said on Tuesday night. Meanwhile, NBN Co would keep installing fibre all the way into households throughout 2014.

Dr Ziggy Switkowski, executive chairman of NBN Co, during Budget Estimates at Parliament House. Credit:Alex Ellinghausen

"One key advantage of fibre to the node is that the network can be built and completed more quickly and less intrusively and less expensively than an all fibre network," Dr Switkowski said.

"So yes, fibre-to-the-node should see us provide [broadband] access to Australians at the 25 Mbps level faster than virtually any other fixed network option. The transition ... to a fibre-to-the-node architecture will take most of next calendar year to execute. So we will be fibre-to-the-premises from now well into next year, and then you could say the starting date for fibre-to-the-node at scale will be quite late next year. So to have until to the end of 2016 is a very, very tight timetable."