Opposition Communications Minister, Malcolm Turnbull, has done an about-turn and finally agreed that the Governments accounting treatment of National Broadband Network funding is correct.
In his website blog, Mr Turnbull says:

As far as the balance sheet point is concerned, let us just cut through the fog of spin and nonsense here. A dollar saved on the NBN Co build is a dollar less for the Commonwealth to borrow and service with interest. Under the accounting rules the expenditure on the NBN does not count towards the budget outcome so much deficit or surplus but it is cash real money nonetheless and it does add to the debt burden of Australians.

[6 September 2012, www.malcolmturnbull.com.au/blogs/malcolms-blog/a-response-to-the-technology-spectator/]

This acknowledgement comes after years of misleading claims by the Opposition that the NBN should be classified as an expense under the Federal Budget.
But, as Mr Turnbull has finally realised, building the NBN is an investment that generates a return and this is why the Governments investment in the NBN is classified by budget and international accounting standards as an equity investment, rather than a budget expense.
This treatment is consistent with long-standing budget treatment applied by this and previous governments and is in line with international accounting standards.
The Government, government departments and the Parliamentary Library have been pointing this out for years, yet the Opposition has failed to grasp how the budget works.
Will Tony Abbott, Joe Hockey and Andrew Robb take the advice of their communications spokespersons and end their misleading and negative campaign against the NBN?