The Chief Ombudsman will investigate the Security Intelligence Service and its decision not to disclose whether it has issued surveillance warrants against New Zealand journalists.

The agency declined a request, lodged earlier this year by Newstalk ZB, after its counterpart in Australia revealed it had conducted surveillance on Australian journalists under that country's security laws.

The SIS declined to reveal its practices. Director Rebecca Kitteridge said the agency doesn't release other information about intelligence warrants, as it could potentially jeopardise investigations.

Newstalk ZB challenged the denial.

The Office of the Ombudsmen has confirmed will look into the matter, and has already asked the SIS to provide certain information about the decision not release the information.