The Coalition's cheaper and slower alternative to Labor's national broadband network has been labelled a ''nonsense'' by experts, who argue it will put Australia behind the rest of the world.

Announcing the Coalition's alternative NBN policy on Tuesday, opposition communications spokesman Malcolm Turnbull promised to build a cheaper, slower network, sooner.

A comparison of the plans.

Under the Coalition's plan, broadband speeds will be slower than Labor's NBN, but ''more than enough for the average household'', Mr Turnbull said.

''As you go higher and higher, the things you can do with that speed are less and less in a residential environment,'' he said.