Mr Laws said he had verbally informed chairman Andrew Noone and his council colleagues of his decision about three weeks ago, but officially resigned last Friday.
He said considering the 2022-23 draft annual plan, and the 18% projected rates rise, "I realise that I am not fully aligned with the current ORC direction, and nor with the intended employment of an additional 30-odd staff".
"I am, as you will be aware, far from aligned with the senior staff presentations/arguments that were presented at our last special workshop/meeting," his letter said.
"I realise that a deputy chairman needs to publicly promote/defend a plan even if it doesn’t accord with their views but think [2022-23] will be a step too far for me.
"I have every intention of representing the cares and concerns of my Dunstan ward constituents as passionately as possible."
Mr Laws said in a media statement that as deputy chairman, "you are expected to promote the council’s plans, even when you fundamentally disagree with them".
The proposed rates hike, along with a $190-an-hour consenting charge, was a "step too far", he said.
He had opposed the draft annual plan going through last month, unhappy that "in the midst of a cost-of-living crisis" ORC was adding to it.
"At that point, the proper thing to do is for me to step aside and advocate both publicly and politically for significant change."
A new deputy will be elected at the next ORC meeting on May 25.
