The smelter, part of the aluminium giant's Pacific Aluminium portfolio, which RTA would very much like to sell off, has been under the cosh for some time.

Depressed prices and high spot electricity prices and the fact that Tiwai is still engaged in talks with Meridian, its power supplier, are all too familiar signs that all is not well and that the smelter's 800 jobs could be a risk.

Pacific Aluminium's chief operating officer Brian Cooper is said to be working with employees to improve operations and protect jobs.

Rio Tinto New Zealand owns a 79% stake in the facility and made an operating pre-tax loss of $91.5 million, excluding the write-down.

Closing the Tiwai plant would cost Rio Tinto Alcan $400 million.

Last year, the departure of Tom Albanese as Rio Tinto's CEO, was a direct result of substantial write-downs of the company's global aluminium and coal assets.

Sam Walsh replaced Albanese in the top job.