Investigations have uncovered more details on an $80 million water sale to a Cayman Islands company established by Energy Minister Angus Taylor.

New reports suggest the Coalition paid the tax haven-linked Eastern Australia Agriculture nearly double the recommended value for water licences.

It now appears that most of the record $80 million sale profits were sent to Eastern Australia Irrigation - a Cayman Islands company established by Energy Minister Angus Taylor.

Former deputy PM Barnaby Joyce approved the deal in his role as water minister in 2017.

A valuation by Colliers International has been obtained by independent senator Rex Patrick.

The valuation appears to contradict Australian National Audit Office (ANAO) findings that the Commonwealth’s strategic water purchases were less than the maximum price recommended by valuers.

The document gives a valuation range of $1,100 to $2,300/ML, with a central estimate of $1,500/ML for licences attached to Eastern Australian Agriculture’s properties in Queensland.

The Commonwealth paid the company $2,745/ML, which is nearly double the valuer’s central estimate and 19 per cent higher than the top of the valuation range, according to analysis by Slattery & Johnson for The Australia Institute.

“Australians should be disturbed that their money has been spent paying well over the market price for these water licences. It’s no wonder the government went to such great efforts to keep the valuations secret,” Senator Rex Patrick said.

A spokesperson for the Department of Agriculture, Water and the Environment has defended the deal.

“The price paid for overland flow water entitlements purchased from Eastern Australia Agriculture in 2017 was informed by an independent market valuation,” the department said.

“While the valuation was $1,500/ML with a market value range of $1,100/ML to $2,300/ML, the valuation also stated that the department should be prepared to pay 10 to 30% above the standard market rate (i.e. up to $3,000/ML) for ‘properties of a high standard that have achieved above average levels of water use efficiency’ in this region.”

The licences described by Colliers’ valuer Shaun Hendy were for “lower valued” water.

In regard to the alleged “above average levels of water use efficiency”; the properties in question were assessed as being the worst performing of comparable properties. Their measures of efficiency were just 39 – 47 per cent, which is far less than many higher-performing irrigation operations in the region.

Australia Institute research director Rod Campbell says there is deliberate obfuscations going on.

“Prior to the unredacted version being released, Department of Agriculture officials selectively quoted and misrepresented this valuation to suggest that a premium would need to be paid to the vendor due to the efficiency and quality of these properties,” he said.

“We now see that rather than the EAA properties being the best in the region, they are actually among the worst performers in various valuations and had rapidly increasing liabilities.

“The public has a right to know why so much was paid and who was responsible for paying so far above the valuation the department commissioned,” Mr Campbell said.