Under changes flagged by Mr Barnett, shops would be free to open 9am on Sundays, with considerations being made to cut weekend penalty rates.
Sunday trading is currently allowed from 11am.
"There's no doubt people like weekend shopping and Sunday has become probably the third most important shopping day in terms of revenue," Mr Barnett said.
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READ NOWCCI chief executive Deidre Willmott said the commitment would make WA more liveable and people-friendly.
"CCI has long campaigned for the deregulation of retail trading hours on the grounds that business owners should decide when their business should open, not governments," she said. "These reforms would create employment opportunities, increase economic activity, lower the costs of doing business and improve convenience for residents and tourists."
Perron Group property investments general manager Andrew Byars said Cockburn Gateway would take advantage of all available trading hours.
"It's a positive for working families and busy people, giving them extra time over the weekend to shop," he said.
"And it's a positive for retailers, giving them the opportunity to open when customers would like to shop."