Prime Minister Tony Abbott guaranteed all Australians 50 megabits per second download speeds by the end of the decade on Thursday. There's just one problem - it's not going to be possible.

The Prime Minister made the claim in a press conference when asked whether the government would consider reprioritising the NBN rollout to assist northern Australia, which he was releasing a white paper about on how it can prosper and be developed over the coming years.

"What we have made clear as part of the NBN is that within a very short space of time, certainly by the end of the decade, that everyone will have access to I think it's 50 megs download speed, or better. So, this is the commitment that we have made and this is the commitment that we will keep," Mr Abbott told reporters.

But Communications Minister Malcolm Turnbull's statement of expectations to NBN Co, the company building the national broadband network, doesn't actually guarantee this. It states that all Australians will be guaranteed 25 megabits per second speeds when they get the NBN. No timeframe is stipulated either, with it saying that NBN should be built "as soon as possible".