Greenpeace suspects it may also have been spied upon by a major corporation.

Solid Energy has defended its decision to hire an investigations company, which planted a spy among the Save Happy Valley Coalition which is protesting against the state-owned enterprise's open cast mining on the West Coast.

Greenpeace alleges Mighty River Power may also have hired the same private eye company last year, when Greenpeace was fighting the SOE's bid to refire the Marsden B coal-fired power station in Northland. Greenpeace says it has been trying for some time to find out what information Mighty River had on it, including anything gleaned by private investigators. The issue is now before the Ombudsman and the Privacy Commissioner, after Mighty River refused the request.

Prime Minister Helen Clark has said Solid Energy's actions were unacceptable and State-owned Enterprises Minister Trevor Mallard will be talking with the company.

But Solid Energy says it acted legally and morally by getting intelligence on the Save Happy Valley group and had a duty to protect its staff and business against increasingly illegal actions.