As another unfortunate police paid informant was outed over the weekend I was reminded of another day in 1985. The day the Rainbow Warrior was bombed by the French secret service killing our photographer and crew mate Fernando Pereira.

Greenpeace NZ had had a French spy working in the office posing as a volunteer for a month or more before the bombing. Everyone she had stayed with and who extended their friendship to her felt used, very betrayed and very angry.

I have often thought that had the French government's attempt to stop Greenpeace been successful, it would have been because Greenpeace became a suspicious, closed and paranoid organisation as a result of that betrayal. Thankfully we didn't. We remained open and up front about what we do, why we do it and how we do it. That's a fundamental right in a democracy and we need to keep practicing it if we are going to keep it healthy and alive. Protest and dissent are an essential element in a democracy. The police have crossed a line with this ugly deception and seem increasingly inclined to do so.

Once you start spying on your own people you become no better than those you claim to protect us from. Look at how sadly and extremely the US has done this in the last five years. In the name of stopping terrorism, laws are bent , people are jailed for years without charge, with no right to legal representation and no idea why they are being held.

How easily the line can be crossed -- sometimes even without noticing. Suddenly you are no longer the righteous upholder of human rights but the very destroyer of them instead.

The NZ police have overstepped the line in paying people to spy on local community and environmental groups. Yes surveillance is something you expect the police to be doing but this kind of dirty business is poisonous. It undermines people's trust in each other and in the kind of relationships that many of us have with those in authority.

You have to wonder whether there isn't something better the police could be spending their money on.

Bunny McDiarmid Executive director Greenpeace New Zealand