"They've seen their pay go backwards by thousands of dollars and it's not as simple as getting another job," the union's national secretary Jo-ann Schofield said ahead of the campaign launch in Brisbane on Sunday.
"It's as if those workers don't matter."
The independent Fair Work Commission reviewed penalty rates and then decided to cut them, with the first round taking place in July 2017.
Labor leader Bill Shorten was then a minister when he played a role in getting the review started, and later said he would accept its decision.
He now wants to restore penalty rates if he is elected, while Mr Morrison has said Labor won't be able to pay for it.
United Voice says the rates slash has impacted 700,000 individuals working in retail, hospitality, fast food and pharmacy.
When the final trim takes effect in July a hospitality worker on an average eight-shift will have lost $40 a shift, or around $2000 a year, it says.
"The economics evidence shows people who are on middle or low incomes spend pretty much every cent," Ms Schofield said.
She says restoring wages will bump the economy, particularly in regional areas, because people will have more to spend.