"So what is the figure?" asks Mr Allen.
Federated Farmers is strongly opposed to a water royalty when it would essentially be an extra tax on electricity, food and exports.
"If the problem is with bottled water, then let's just fix that problem."
If we're going to go wider, then for a tax to work it must be applied to all sectors - not on the selected targets of officials and politicians.
"We have done our numbers - a simple calculation based on publicly available information.
"If it's 10c per litre, it looks like this: $1600 billion for electricity (Manapouri); $600 billion for food production; $100 billion for fruit, vegetables, wine and bread; $15 billion for Auckland's water.
"Even if these figures are a thousand times exaggerated - and Labour has said a charge for irrigation will be per 1000 litres rather than per litre - then these billions become millions."
Mr Allen said if the principle is to charge large commercial users, that has to apply to Manapouri also because that scheme diverts Southland's fresh water that after generating electricity goes straight to the sea. It accounts for 60 per cent of consumptive water use.
"And then what do you do for the Waikato people - do you force then to pay for the use of their water but allow the electricity companies and Auckland to get it for free?
"Some 95 per cent of the Waikato's water is locked up for electricity generation and is only available for other uses at the bottom end of the river."
Mr Allen says in terms of bottled water, it's pleasing that Labour has picked up on Federated Farmers' idea that we require foreign-owned companies which extract water for bottling to pass the 'net benefit to New Zealand.