The Government has conceded it has no idea how much it will cost to sell shares in Meridian Energy.
During Parliament's Question Time ministers were asked what estimates had been done on the cost of allowing individual investors delay paying the full cost of their shareholding for 18 months.
Radio New Zealand's political editor reports that ministers replied the Treasury had done no work on the matter.
Under the sale investors will pay 60% up front for the shares but then have another 18 months to pay the balance.
Labour Party State-owned enterprises spokesperson Clayton Cosgrove asked Mr English about the cost of the sale and what work Treasury had done on the cost of the sales process.
Mr English said none because it wasn't possible to determine the cost without knowing how much the shares would sell for, and without knowing that it would just be a guess.
Green Party co-leader Russel Norman then questioned the State Owned Enterprises Minister, Tony Ryall and said rich investors will effectively get a $100,000 interest-free loan from the Government to buy shares.
Mr Ryall said the instalment plan will provide New Zealanders with an opportunity to take a bigger stake in the company than they might have otherwise.
Labour and the Greens believe the instalment scheme for the Meridian sale will cost taxpayers about $40 million.
But Mr English disputes that figure even though he has no idea what it will cost.