The cuts come because the cleaners - who are employed by contractor Medirest - at the hospital have been classified as hospitality workers.

Union United Voice puts the blame on the ACT government for choosing to outsource - instead of making them ACT public servants - all non clinical staff at the new hospital when it opened last year.

The union said the hospitality classification defied logic and was an attempt to piggyback on the penalty rate cut gradually going into effect for people on the Hospitality Award. It said the award covers workers in restaurants, accommodation and catering - not hospital cleaners.

Hospital operator Medirest has given staff a two month reprieve with the rate due on July 1 now coming on September 1.

United Voice ACT branch secretary Lyndal Ryan said the situation was largely the fault of the government's "privatisation by stealth".

"It has been an anxious time for support workers at [the hospital], frustrated by the fact that they have been waiting for 12 months to win what the community expects them to be paid," she said.

"The ACT government needs to take responsibility. They must ensure that the appropriate pay and conditions are provided to the staff providing the services at the hospital. The government should definitely not be overseeing penalty rate cuts - delivering pay cuts to the hospital's weekend workers does not meet community standards."

Ms Ryan said when the hospital opened, Health Minister Megan Fitzharris gave the union an undertaking the government would meet any shortfall between what Medirest offered and what workers should be paid to meet community standards.

She said the contractor denies having been given any commitment from government that they will fund fair wages.

Ms Fitzharris declined to answer a number of questions, instead her office redirected questions to Canberra Health Services.

"The ACT government supports maintaining penalty rates for workers and urges the parties to continue to negotiate to come to an agreement as soon as possible," a Canberra Health Services spokesman said.

Hospital cleaner Taina McDonald said she was a single mum earning a living working nights and weekends.

"Now at the hospital they are planning to cut our penalty rates for weekends in just two months," she said.

"I work shifts that mean my health, family and social life suffer.

"I do these shifts for the penalty rates so I can pay the bills, and it can't be forgotten that this cleaning work is really vital to the hospital running effectively."

Ms Ryan said improper use of the hospitality award and penalty rate cuts were exactly what the union was warning about when it objected to hospital staff being outsourced to private contractors.

She called on the government and Medirest to immediately take action and commit to protect penalty rates.

A Medirest spokeswoman said the company was currently involved in an enterprise agreement negotiation with staff at the University of Canberra Hospital.

"We continue to negotiate in good faith," she said.

"It is not appropriate to speculate on the outcome of the agreement at this time."