But National's Transport spokesman Paul Goldsmith said it was a "radical" plan that is an "over-reaction that would prove deeply frustrating for Aucklanders".
He said the plan would mean a 40 per cent speed reduction in major Auckland roads, such as Hobson and Nelson street.
He said it was "anti-car zealotry" and called on Aucklanders to push back on the plan.
Ellison said setting safe speeds is one of the quickest and most effective tools there was to reducing road trauma.
But Goldsmith said this argument is hard to understand, given cars have never been safer than they are now.
In 2017, 28 people died in speed-related crashes. Historically, inappropriate speed has contributed to more than 20 per cent of all deaths and serious injuries on Auckland's roads, according to AT.
Goldsmith said other factors that contributed to the spike in accidents in Auckland last year should be considered before lowering the speed limit in the CBD.
He said these include the enforcement of current rules around drink driving, red-light running, drivers distracted by cell-phones, not wearing seatbelts, driving under the influence of drugs and exceeding current speed limits
Goldsmith is not alone in his opposition to the proposed rules.
The Automobile Association (AA) is urging AT to take a more balanced approach to safety.
AA spokesman Barney Irvine said there is strong justification for slower speeds on most CBD roads on safety grounds, but the AA would be pushing for reductions to 40km/h, not 30km/h.
He said Sydney and Melbourne have both moved to 40km/h CBDs to good effect.
"Telling people to drive at 30km/h on wide, expansive roads that have a natural driving speed of 50km/h just won't work – all that's likely to happen is that people drive above the limit at the speed that makes sense to them."
AT is now asking for public submissions on its speed reduction plan.
Any proposed speed limit changes would come into effect later in 2019 following consultation in February and March, and adoption of the bylaw.
