The builder of the National Broadband Network has admitted it is prioritising mass rollouts while bypassing complex cases, prompting federal Opposition criticism that it is trying to make the Government look good.

About 98,000 premises in Australia are categorised as Service Class 0 with no basic phone line.

They are complex cases, typically homes and businesses built on vacant blocks with no previous phone connection, in suburbs where the NBN has rolled through.

The head of the NBN has confirmed Service Class 0 connections may have to wait years while mass rollouts are fast tracked.

"If we can do 100 homes in a day versus that same amount of resource doing three or four, we are going to wait on the three or four, get the hundred in and eventually come back after we have these big swathes of homes that are connected," chief executive Bill Morrow told a recent Senate committee meeting.

"We made the commitment it will be done by 2020. It could well be that we are coming back to address that home next year or even particularly the year after.

"It is our objective and desire to have everybody connected as soon as possible and we know how frustrating it can be."

Speed and volume the focus

Under questioning from Tasmanian senator Anne Urquhart, Mr Morrow conceded the installations were in the "too hard basket" and that speed and volume was the focus.

Regional Communications Shadow Minister Stephen Jones said the NBN Co should not be allowed to leave almost 100,000 premises without phone and internet.

"There's a rush out going on here when it should be a rollout," Mr Jones said.

"We are saying very clearly to the NBN and the Government there needs to be a plan to fix this."

"We think it is wrong and what's going on here is the NBN is desperate to ensure they make Malcolm Turnbull look good by meeting his artificial rollout targets, and the result is they are rushing past premises, they aren't stopping to fix the more difficult cases."

Mr Morrow denied the claim, saying engineering teams had made the decisions around complex connection cases.

"The Government is not involved in this. Again, the remit that we pass down to our teams is 'get the volumes through on this thing' because the more people we connect, the faster, the better off the people of Australia are going to be," he said.

The number of Service Class 0 premises is expected to grow as the NBN rollout proceeds.