Michael Donovan, of the Shop, Distributive and Allied Employees Association, has written to the Fair Work Ombudsman after delegates reported many workplaces were not recognising the newly created public holiday and their obligation to pay staff up to double-time-and-a-half.

"The position is clear – it is a public holiday and public holiday penalty rates apply," Mr Donovan said.

The letter requests the ombudsman to widely publicise to retail and fast-food industry employers that Easter Sunday is a public holiday, and conduct "widespread inspections" to ensure penalty rates are paid.

"Some of our members have been told they have to work on Easter Sunday and it's not a public holiday … this is nonsense," Mr Donovan said.

The Andrews government's decision to create two new public holidays – on Easter Sunday and Grand Final eve – prompted an angry response and strong warnings from employers.

Retail and hospitality lobby groups urged the government to rethink the decisions, which were election pledges, saying they would force businesses to shut their doors.

A spokesman for the ombudsman said the agency had an important role in educating employers and employees about their workplace rights and obligations, including public holiday entitlements.

"This week, the agency issued a call to employers and employees across the country to check the pay rates and entitlements that apply over the coming Easter public holidays," he said.

Ombudsman Natalie James said most underpayments were inadvertent and the result of employers failing to check their legal obligations, "so it's important employers take the time to get it right this Easter".

"It is important for employers to be fully aware of the minimum pay rates that apply to their employees," she said. "Otherwise they can end up facing bills for back-payment of wages they weren't budgeting for."