During the last government and the Thatcher one that preceded it, government did its best to take as much government spend off balance sheet (ie so it wouldn't show) through a series of Private Finance Initiative (PFI) and Public Private Partnership (PPP) deals. Yes we know that we, and our children, and our children's children will be paying the bills for decades.
In the meantime, here's a methodology to make sure that it doesn't happen again http://www.bereal.salford.ac.uk/index.htm
This describes a Benefits Realisation methodology that isn't new (it's a combination of most of the well-known existing benefits realisaton methodologies, some of which are widely discredited so don't get too excited) but it is gaining credibility with OGC which could be valuable.
Worth a look? Let me know!