The law gave some retailers an unfair advantage over others, Mr Johnston said, because "it's filled with exemptions that render it meaningless".
"A corner dairy can open, but not a supermarket. You can go shopping in Queenstown or Taupo, but not Wanaka or Rotorua. A shop can be filled with workers packing internet orders - but it can't open the front door to the public. None of these restrictions make sense in 2015."
Retail NZ would write to the Government asking for changes to the law, he said, with an aim of bringing in new legislation in time for Easter 2016.
"I'm not saying every shop must open, that everyone must shop, or that everyone must work - but if people want to, why should the Government get in the way?"
Meanwhile, at least two retailers have vowed to defy the Easter trading laws.
Oderings director Darryn Odering said all 10 of its stores - five in Christchurch and five in the North Island - would open over the weekend.
The garden centre chain has opened every Easter weekend since 1972, Mr Odering told Newstalk ZB, and this one would be no different.
Easter trading laws were outdated, Mr Odering told the station, and needed to be changed.
Rival garden centre company Kings Plant Barn has also declared it will open all weekend.
Bob McCoskrie, national director of Family First, said workers deserved to take a break and spend time with families and rejected calls for liberalisation of Easter trading laws.
"This is not an issue about choice as has been argued.
For many workers, they don't have the luxury of choice as to whether they work or not," he said.
"Easter, Christmas and Anzac Day each remain as one of the few times when the whole country stops and takes a break."
He said the law needs to be consistent, fair and be strongly enforced.
He singled out "renegade gardening centres" as the kind of retailers flouting the law, and called for the Ministry of Business, Enterprise and Innovation to enforce the legislation.
