Malcolm Turnbull has promised not to remove the NBN cables already in the ground if the coalition wins office.

Mr Turnbull, the opposition's communications and broadband spokesman, will address the National Press Club on Wednesday and is expected to outline the opposition's alternative high speed internet policy.

His address comes as the company delivering the federal government's national broadband network (NBN) announced it will start work on another six new sites in Queensland, NSW and the ACT over the next six months.

The NBN Co will also extend its current network in Armidale, Kiama and Jamberoo in NSW as well as Townsville in north Queensland.

Mr Turnbull has promised not to tear up the NBN infrastructure should the opposition win power at the next election.