Mr Kirby, who is a Companion of the Order of Australia, said in an interview that he was not ''obsessive'' about animal welfare law.
And New Zealand's animal welfare legislation was more advanced than that of Australia.
Nevertheless, he believed it was time for New Zealand to ensure that the commendable animal protection principles spelled out in its animal welfare law - and based on ''five freedoms'' for animals - were properly supported by accompanying regulations.
Adequate resources were also needed, including sufficient animal welfare inspectors, to ensure the law was enforced.
Although New Zealand had many millions of farm animals, it had relatively few animal welfare inspectors, and a charitable body, the SPCA, had been charged with enforcing the law involving domestic companion animals.
Another ''fundamental problem'' was that, in the course of food mass production, including in New Zealand and Australia, there had been a ''corporatising'' process involving creatures such as hens, and they were being treated as ''things'' rather than as ''living, breathing, feeling'' beings.
New Zealand was a highly efficient food producer and ''should be a leader in the international standards''.
Under a revised animal welfare code, which took effect in New Zealand last December, new battery hen cages are banned and existing cages are to be phased out over 10 years.
He said battery cages allowed hens only the size of an A4 piece of paper to stand in, breaching one of the five animal freedoms, the chance to display normal patterns of behaviour, given hens were social animals.
Costs were involved for the poultry industry but given the ethical concerns about battery cages, he wondered how the practice had ''somehow become tolerable for another nine years''.
Mr Kirby gave an open lecture on ''Animal welfare law reaches a moment of truth'', at the University of Otago on Tuesday night.
New Zealand is updating the Animal Welfare Act (1999), and, after public submissions closed last year, the Government is expected to introduce proposals for a revised law later this year.
