A new website has been launched to promote the adoption of a written constitution for New Zealand.

The site, http://constitutionaotearoa.org.nz, promotes a forthcoming book by Sir Geoffrey Palmer QC and Andrew Butler.

Their book, A Constitution for Aotearoa New Zealand, will be published by Victoria University Press on 21 September 2016.

The website states that the objective is for "a modern constitution that is easy to understand, reflects New Zealand's identity and nationhood, protects rights and liberties, and prevents governments from abusing powers".

A media statement issued by Sir Geoffrey says the book aims to provide a model and stimulate the debate.

"The changes we will put forward we believe are a necessary part of preserving democratic freedom in New Zealand, and of protecting the fundamental principles which anchor public power and strengthen government accountability. We want to find out if New Zealanders agree."

Sir Geoffrey says New Zealand's present constitution is incomplete and far too flexible. Unlike most other countries, nearly all of New Zealand's constitutional rules can be altered very easily by Parliament, he says.

"In our view, government should be conducted under the law. That law should apply to everyone, including Parliament. People have rights and they should be provided in a constitution that is supreme law and binds the Parliament."