"It lacks a long-term plan for policing and significant gaps remain in its understanding of demand for police services and their costs.
"The way the (Home Office) chooses to distribute funding has been ineffective and detached from the changing nature of policing for too long, and it cannot be sure overall funding is being directed to the right places.
"With plans to reform the funding formula on hold, and no systematic approach to ensuring forces are financially sustainable, we cannot conclude that the Home Office's oversight of the police system is value for money.
Mr Macpherson said: "I have been pressing the case with ministers at every opportunity for Wiltshire Police to get a fair slice of the funding cake. The NAO agrees that reform of funding is needed
"We all face the same complex range of threats, a fact brought home to us all very powerfully with the Salisbury chemical weapon attack
"We get £151 per person to spend on policing. The national figure is £171. It does not make sense to give policing in Wiltshire £20 less per person than the national average
"Even if you compare us with similar forces, the difference remains stark: £17 less per person each year.
"The Home Office did the right thing last year in giving PCCs flexibility to increase the policing element of council tax by up to £12 a year. I trust that it will do the same in 2019.
"Last year's increase allowed me to protect community policing team numbers across Wiltshire and Swindon. I need to do the same again next year. Officer numbers should not fall any further.
"The Government needs to reform the formula which allocates funds to me. We have been historically under-funded and the people of Wiltshire and Swindon deserve a fair deal."