Prime Minister Jacinda Ardern is staying tightlipped over her dealings with major multinational companies about datacentres being built or planned for New Zealand.

Her office has rejected an Official Information Act request by RNZ for briefings to Ardern ahead of any meetings with the companies Amazon Web Services (AWS), Microsoft, DCI, Datagrid, CDC, Lake Parime/ Simply Energy, Google Cloud, Salesforce, Catalyst Cloud, CCL and Datacom.

Previously released documents show many of the companies have been strongly lobbying ministers for support.

For instance, they show AWS "posed several requests as part of its investment commitment" which it puts at $7.5 billion over 15 years, and had direct contact with the prime minister.

RNZ asked for any briefings about energy supply, energy resilience or government agencies being potential customers of a data centre.

Ardern's chief of staff replied that briefings existed but would not be released.

"These briefings are provided to the prime minister in confidence, to support her in her role as leader of the government and chair of Cabinet," Raj Nahna wrote.

Read the response from the prime minister's office (PDF: 110KB)

"These briefings are withheld in their entirety, including titles and dates," citing four reasons under the Act including: "the release would likely prejudice the international relations and/or national security of New Zealand".

Datacentres use a lot of power.

Datagrid previously wanted to use electricity left surplus if the Tiwai Point aluminium smelter - which gets the power at cut-price rates - was to close. This was before the smelter decided not to close.

Documents have also showed that officials expected Datagrid to "propose the data centre as a backup for government data".

A lot of government data is stored in Australia in the 'cloud' - meaning in this case on Microsoft datacentre servers.

RNZ also asked for any communications between Ardern and any other minister that referred to datacentre energy issues or agencies as customers.

These also existed, Nahna said, but consultation with the organisations was ongoing, so the information could not be released yet.

He also transferred RNZ's requests to the Department of Prime Minister and Cabinet.