Bill Shorten is standing firm and vowing to reverse a decision to cut Sunday penalty rates for some workers as changes come into force.

Sunday marks the first day some workers’ rates will be cut following a February decision by the Fair Work Commission, affecting employees in retail, fast food, pharmacy and hospitality.

The Opposition Leader used a rally in Caboolture in Queensland to repeat his pledge to reinstate penalty rates within 100 days of taking office.

“I will protect workers’ take home pay and I will also reverse the tax cuts for millionaires which Malcolm Turnbull gave them yesterday,” he told reporters.

The government insists the decision to align Sunday rates with Saturday was made by an independent umpire, which was set up by Labor when it was in power.

But Mr Shorten said the opposition now wouldn’t be standing by and seeing the pay packets of workers reduced.

“I ask Malcolm Turnbull, how much harm has to be done before you will decide to stop using that fatuous ‘leave it to the umpire, wash my hands of the problem’ approach?”

The issue would be left up to the biggest independent umpire – the Australian voters – at the next election, Mr Shorten added.

Shadow Treasurer Chris Bowen added his voice to the criticism, telling reporters in Sydney it was the first time since the Great Depression that workers had received “a pay cut such as this”.

“Not as a part of bargaining, not as part of a trade-off, but a straight pay cut,” Mr Bowen said.

Lawyers have reminded workers to check their pay slips to make sure they aren’t being short-changed.

The cuts to Sunday rates will be phased in over the next few years and won’t fully hit hospitality and fast food workers until 2019 and retail and pharmacy workers until 2020.