Who do I contact to renew my New Zealand passport in Australia

Go to the nearest post office and ask them for the address of The New Zealand High Commissioner in CANBERRA, ACT.
Then write to him for full details.

Head on over to The New Zealand Department of Internal Affairs website (link below). All of the information you need to renew your passport is listed there, along with application forms and fees (in both Australian and New Zealand currencies). There is also information there for those living in other countries who want to renew a New Zealand passport.

The only problem I have found with the renewal is the witness for the application. This person needs to be a New Zealand passport holder, have known you for over a year, not be a relation or living at the same current address as you and must also be a registered professional (e.g. judge, lawyer, optometrist, nurse, etc). I have not found any luck with a solution so far, so the best advice I can give is to ring your local New Zealand Embassy and ask them.

The links needed are provided below:

The New Zealand Department of Internal Affairs:
Homepage: http://www.dia.govt.nz/
Passport application and renewal: http://www.dia.govt.nz/diawebsite.nsf/wpg_url/services-passports-how-to-apply-for-a-new-zealand-passport?opendocument#eight
Application forms and fees: http://www.dia.govt.nz/diawebsite.nsf/wpg_URL/Services-Passports-Application-Forms-and-Fees?OpenDocument#two

What is the fastest way to renew my NZ passport I'm planning to go back to NZ in a month.. will it be ready by then? Please help me how to renew my passport asap

I don't know any one in Australia who holds a N.Z. passport to ask as witness .

Me and my two kids live in qld australia and our passports have expired where can I renew our passports.

I live in the UK and have exactly this problem. I phoned the High Commissioner (HC) and was told to leave witness blank but fill out a statutory declaration (download from passport application site) instead, stating reasons a witness cannot be found. I will personally take my application to the HC who will witness the statutory declaration for me free of charge.