Labor says its National Broadband Network will deliver internet speeds 10 times faster than first thought, at 1 gigabit per second.

Prime Minister Julia Gillard and Communications Minister Stephen Conroy are in Hobart today to officially launch the first part of the national fibre-optic broadband network.

When the Government first unveiled the $43 billion NBN plan it promised to deliver speeds of 100 megabits per second (Mbps).

But Senator Conroy now says fibre-optic speeds will hit 1 gigabit per second, 10 times faster than first thought.

"The announcement by NBN Co to increase capacity on the network shows that fibre technology is truly about future-proofing the nation," he said.

NBN Co chief Mike Quigley will outline further details in a speech in Sydney later today.

The announcement comes just 10 days before election day but Senator Conroy said he was only told of the increased speeds last night.

Senator Conroy was also quizzed on whether it was known all along that the network was able to deliver much faster speeds than the originally announced 100Mbps.

"They're now confident that they've actually robustly tested it, that the interfaces can sustain the gig," he said.

Opposition Leader Tony Abbott says he doubts the Government's claim of super-fast speeds.

"This idea that, hey presto, we are suddenly going to get 10 times the speed from something that isn't even built yet, I find utterly implausible," he said.

Ms Gillard used the NBN launch to attack the Coalition's decision to scrap it.

"I am completely determined that we will build the NBN," she said.

"I will build the NBN. Mr Abbott, if he is elected as PM will not. That decision would cost Australia jobs."

The Government says the NBN will provide fibre-optic connections to 93 per cent of the population. The remainder would receive wireless or satellite technology.

The Coalition also revealed its broadband policy this week, pledging to spend $6 billion to deliver internet speeds of up to 100Mbps to 97 per cent of Australians through a range of technologies.

The Coalition has vowed to dump the NBN because it says it is too expensive and it does not support a nationally owned network.