Comments on David Uren “Swan searches for a surplus strategy”, 10/01/2013, http://www.theaustralian.com.au/news/swan-searches-for-a-surplus-strategy/story-e6frg6n6-1226550691942
It seems a mutually accept method for the most appropriate resourcing of the PBO is to make a law before an election and make that law effective after the election, so whoever is in the government of the day does not matter much. Then any changes to that legislation should meet a stronger and more stringent condition than simply majority in both houses.
For example, have a legislation to cap the ratio of government revenue to GDP, as well as certain accountability of government policies, can all be made in such a way.
In fact, many difficult policies that may favour or harm the government of the say can be made in such a way to neutralise its effects on the government of the day, but binding on future governments.