No explicit ban. But if state servants are to support party politics (especially during campaigns) certain restrictions apply.
"State servants must ensure that they do not confuse their political rights with their employment responsibilities. State services agencies must ensure that they respect the political rights of their employees and do not impinge on these rights beyond what is lawful. These principles apply at all times but special care must be taken in an election period. It is also a well-established convention that stricter requirements apply to State servants who:
- are very senior; have regular direct contact with Ministers; or represent a public face of their agency
- work in a Minister’s office, or
- are actively engaged in providing advice to Ministers on an issue that is the subject of political activity.
These State servants should avoid active involvement in political activity if it could be perceived as conflicting with their political neutrality obligations."
Source: Electoral Act 1993, (amended 2020)