Consulting ecologist Mark Bellingham is questioning why councils are insisting the Government bring in cat control laws.
He told Newstalk ZB animal control regulations are managed by councils.
"Are the councils too wimpy to do anything and they're going to dump it all on government to carry out what they should be doing themselves?"
He hadn't seen any good evidence to show collars really make a difference, with some cats working out how to move so as to not have the bell ring on their collar.
"Except they could get caught and then you have an issue of cruelty to a cat."
The idea of a "cat curfew" which would result in owners locking their cats inside at night was another unsupported solution, he said.
"The thing is, you're talking about cat curfews, well the size of the evidence is actually not very good on that, because it seems that at night cats are actually really good at getting rid of rats and mice. That's the bulk of what they take."
They tended to hunt birds more during the daytime.
As for an idea to employ "cat rangers", Bellingham could not see how the plan would work.
"The cat ranger thing sort of sounds like someone out there with their six shooter saying 'make my day'. I'm not sure how well that's going to go down."
Bellingham said it would likely end in the cat ranger covered in scratches or "disappointed" as the cat they were nabbing retreated higher and higher up a tree.
"I really need to see a coherent plan," he said.
Councillor Kate Wilson said yesterday she did not want to prejudge what any legislation would look like, but she imagined any cat registration introduced would be a one-off cost at the time of microchipping and desexing.
''Once it's done, it's done.''
The legislation may give the council the power to destroy cats that were not chipped.
''At the moment it is the only animal that is not legislated for, and it's peculiar.''
Wilson said people who were concerned about the proposal ''should be weighing up the concerns they have if you don't have it''.
''If you get rid of the stoats and rats and weasels, what are the cats going to live on if you don't manage them?''