More than a thousand jobs will be lost with New Zealand's only aluminium smelter set to close.

Rio Tinto has announced its Southland-based New Zealand Aluminium Smelters company will wind up operations in August 2021.

The Tiwai Point plant employs a thousand workers directly, and has created 1600 jobs in the wider community.

Rio Tinto Aluminium chief executive Alf Barrios says they recognise what a significant impact this will have on staff and the region. But he says the outlook for the industry is bleak, and energy costs are far too high.

The smelter operated at a loss of $46 million last year.

Meanwhile, the Government's announced there will be a permanent police presence at all managed isolation and quarantine facilities.

It comes after two people absconded from managed isolation in Auckland in less than a week.

Air Commodore Darryn Webb says there have been security officers on site - but they don't have the powers to detain people.

He says the integration of police into onsite security teams will ensure necessary compliance.

The Government's also implementing monitored smoking areas at all facilities.

Webb says banning smoking isn't appropriate at this stage - but the areas will be closed if they can't be monitored.

Listen to Clare de Lore and Tim Wilson talk with Heather du Plessis-Allan on The Huddle about these stories and the rest of the day's news