The United Workers Union, which represents the staff, said the Queensland Investment Corporation, which owns the Canberra Centre, had assured workers rosters and employment would remain the same under a new contractor.

But the union said AssetLink, the new contractor, had offered long-term employees vastly different hours of work and had sought to convert people from permanent positions to part-time or casual contracts.

Ronaldo Belo, who has been a cleaner at the Canberra Centre for a decade, said he had been offered a new roster that moved his evening shift to a night shift between 10pm and 6am, which would be severely disruptive for his family and day job.

"At the moment, they said to me, 'If you don't want the full time, if you want to go to the casual.' ... At the moment we have lockdown. I don't have any work, because also the second job is also lockdown. So I will prefer to think about everything now," Mr Belo said.

Mr Belo said he continued to ask or a shift to the roster and said many of the cleaners in his department were struggling.

Canberra Centre security guard and father of nine Deng Duoot Ayual, who has worked at the shopping centre for six years, said he would be converted from a full-time employee to a casual after the contract changed over.

"What I have to hope is when the lockdown's gone, they'll give me more hours. I'm not sure - maybe. After that, when I see they've put me part time, I can look for another part time security job in the future," Mr Ayual said.

While the new contractor is legally able to offer different terms of employment and rosters, the union said it amounted to a betrayal of staff in a tough lockdown period by the Queensland Investment Corporation, which had previously provided assurances to workers.

Canberra Centre general manager Gary Stewart said AssetLink had agreed it would offer employment to current employees of the previous contractor.

"Canberra Centre is ensuring that AssetLink complies with this commitment, but the details of employment and rostering are a matter for AssetLink," Mr Stewart said in a statement.

Mr Stewart said Queensland Investment Corporation was a signatory to the Cleaning Accountability Framework, developed by the United Workers Union and AustralianSuper to improve labour standards in the cleaning industry.

"If there is any evidence that AssetLink is not complying with its obligations under [Cleaning Accountability Framework], we would urge anyone to bring that to our attention and we will take immediate action," he said

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Mr Stewart said the corporation had consulted with staff and the United Workers Union throughout the contract procurement process.

United Workers Union property services director Lyndal Ryan said the union wanted the chief executive of Queensland Investment Corporation to step in and force the new contractor to guarantee workers' rosters and employment.

"Canberra Centre management promised cleaners and security guards that their jobs were safe when the contract went out for tender," Ms Ryan said.

"We knew, as did our members that there might be some changes but we had no idea that so many people would be offered jobs that on hours that they simply cannot work."

AssetLink has been contacted for comment.

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