The Turnbull government should split up the National Broadband Network and start preparing to sell it off to private companies, according to a landmark infrastructure plan.

The Infrastructure Australia report, which presents a 15-year vision for the nation's infrastructure needs, says the NBN should be privatised in the "medium term".

"In the near term, the Australian government should commission a scoping study to assess the most appropriate approach, structure and timing to deliver a privatised NBN model," the report recommends.

"The scoping study to assess the most appropriate approach and structure for a privatised NBN should include options to efficiently support delivery of NBN services in regional and remote areas that are non-commercial."