"This law is prescriptive and I don't think we should apologise for that," Mr Shepherd said.
"Toddler drowning is an incredible tragedy, it results in a huge toll for our society...the effect of that is catastrophic for the whole family," he told Radio NZ.
Water Safety New Zealand and SafeKids Aotearoa previously told the Herald the changes would cost lives.
Ann Weaver from Safekids feared there would be more deaths if the act was repealed.
"The act is very specific and it works," she said.
"The changes make it unclear what is required so it will be left to interpretation by pool owners and councils."
Matt Claridge from Water Safety NZ added the bill was "ambiguous, vague and poor".
At the first reading of the amendment in Parliament in September, Minister for Small Business Craig Foss said the act had successfully reduced deaths from 10 each year to three but it was "cumbersome for pool owners and councils".
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Current rules under Fencing of Swimming Pools Act 1987:
*1.2m fence on four sides
*Self-latching gate
*Spas and hot pools require fencing
*Three-yearly inspections
Proposed: Part of the Building Act
*Barriers will be "performance based"
*Five-yearly inspections
*No fencing required for spas and hot pools
NZME lp ml