Rafter is the face of the Mantra Group, Australia's second-largest hotel and resort operator, which has launched a new push for the industrial tribunal to slash workers' weekend, evening and public holiday penalty rates.

In its claim to the Fair Work Commission's review of pay and conditions in 122 workplace agreements, Mantra calls for 50 per cent reductions to Sunday pay - from 175 per cent to 125 per cent of the regular rate. It says public holiday pay should drop from 250 to 225 per cent.

"It is our view that the hospitality industry is predicated on a seven-day per week operation and employees seeking work in our industry are aware of that fact from the outset," the Mantra submission said.

Hospitality workers' union United Voice and the Australian Council of Trade Unions have written to Rafter in his capacity as Mantra's brand ambassador, asking him to intervene in the escalating workplace feud.

In the letter, the former world no. 1 is urged to to take a stand against the proposal to cut penalty rates for thousands of workers at Mantra hotels, resorts and serviced apartments Australia-wide.

"That Mantra is arguing to cut the wages of some of the lowest-paid workers in the country when its businesses are expanding and highly profitable is particularly disappointing," the letter said.

Mantra Group, which runs 115 premises in Australia, New Zealand and Indonesia, said it considered the penalty rates system to be a fair and reasonable measure to remunerate shift workers, and "any suggestion to the contrary is not correct" .

"We are currently in discussions with industry bodies to work towards the best outcome for all industry stakeholders," Mantra marketing director Kent Davidson said.

The claims are the latest to draw attention to the simmering feud over Australia's penalty rates system. Employer groups argue penalty rates are too high, no longer reflect community standards and are forcing businesses to close their doors on weekends and holidays. Unions say penalty rates provide critical and fair compensation for those who work unsociable hours.

United Voice national secretary David O'Byrne said the changes proposed by Mantra Group were "out of step" and revealed a "profound lack of understanding of Australians' values and way of life".

"Mantra Group wants a dramatic cut in the wages of the staff on whom the success and survival of the business depends," he said.

ACTU secretary Dave Oliver said people who worked late nights, weekends and public holidays should be compensated, "whether it's playing at Wimbledon or delivering room service at 3 o'clock in the morning".

Tourism Accommodation Australia said penalty rates of up to 275 per cent hurt workers as much as they do employers.

"If a hotel closes a restaurant or cuts back on room service, the worker ... doesn't get the opportunity to work", TAA acting chief executive Carol Giuseppi said.

Pat Rafter could not be reached for comment on Monday.