Over on KiwiPolitico, in the context of the threatened leak of Labour Party membership and donation data, Anita asks:
Why is it that our public servants, often people who take their jobs out of a genuine belief they can make things better, are so confined in their political activities?The short answer to this is "so the public service can do their job properly". At its heart, the public service is about providing advice to the government of the day. In order for them to do that effectively, the government has to be able to trust them. Fairly obviously, that trust cannot exist if they are seen collectively as being staffed by "the other side". Likewise it cannot exist if a senior advisor is publicly or strongly affiliated with a political party. While things may be fine while said party is in power, their ability to do their job would be compromised should power change hands.
It is also a question of professionalism. Public servants are supposed to give free and frank advice, uncoloured by their personal political beliefs. That cannot happen if they are publicly affiliated with a party. It creates at least the perception of a conflict of interest, taints their advice, renders it useless.
In practice, how neutral you have to be depends on high up the ladder you are. The guidelines are laid out in a document called Understanding the code of conduct - Guidance for State servants, under the standard of impartiality. The short version is that if you work in service delivery, or a low-level role, its not a problem; you can belong to, donate to and campaign for a party (though you should still take care not to conflate your private and professional interests, and you should ensure your political statements are not identified with your department). If you're a senior public servant, a manager or someone who regularly provides advice to Ministers, you shouldn't. Even though political donations are normally private (absent totally incompetent IT security), senior public servants should probably avoid them.
The problem, of course, is "how senior"? The SSC will have one idea, Ministers will likely have another. And if the latter demand a witch-hunt against low-level public servants who have exercised their political rights in accordance with the code of conduct, it is the duty of the relevant Chief Executive and the SSC to stand up and say "No, Minister, you can't do that". As the guardians of public service ethics, they also have an obligation to protect public servants from the partisan hackery of Ministers and their political cronies. If they fail to do so, then they will have failed not only those public servants, but the public service as a whole.