E tū union director Finn O'Dwyer-Cunliffe says up to 50 cleaning workers are affected by the proposal.
Twelve of them are casual E tū members who face having their roles disestablished, and five permanent members would be transferred to a new employer under their current terms and conditions.
One worker, who has not been named due to concerns about retaliation, told E tū the proposal has left people shaken.
"It makes me very uncertain. It is very important I am directly employed as I have a family to support."
Venues Ōtautahi, of which Christchurch City Council is the sole shareholder, owns the Christchurch Town Hall and Wolfbrook Arena.
It is responsible for the operation and asset management of One New Zealand Stadium, and manages the Air Force Museum of New Zealand, Apollo Projects Stadium and Hagley Oval.
O'Dwyer-Cunliffe said any new cleaning staff hired by an outside contractor would have no guarantee of the Living Wage.
Christchurch City Council is a Living Wage-accredited employer and directs Venues Ōtautahi through its letter of expectations to pay the Living Wage.
O'Dwyer-Cunliffe claims outsourcing the cleaning would allow the organisation to sidestep that commitment for future workers.
The proposal follows a failed attempt by Venues Ōtautahi management to remove the Living Wage from new starters.
According to E tū, the new One New Zealand Stadium will require up to 250 cleaning staff. Rather than directly employing workers to meet that demand, E tū claimed Venues Ōtautahi is proposing to hand the work to an external contractor. The proposal also flags outsourcing cleaning at the organisation's other venues.
O'Dwyer-Cunliffe says the move is a backdoor attempt to undermine the Living Wage.
"When management tried to strip the Living Wage from new workers and failed, they found another way to do it.
"Outsourcing these roles means future cleaners won't be guaranteed the Living Wage, and the workers who have given years of service to this organisation are being thrown out in the process.
"Venues Ōtautahi says it's too operationally complex to hire 250 cleaning staff directly, but it has managed to hire 500 people in other roles. That doesn't stack up."
O'Dwyer-Cunliffe said the timing makes it worse.
"These are people with families and bills to pay. They deserve better than to be discarded the moment a new building opens."
O'Dwyer-Cunliffe said E tū is calling on Christchurch City Council to ensure its Living Wage policy cannot be circumvented by outsourcing, and One New Zealand as the stadium's naming rights partner to ensure the new venue "is not built on lower wages and fewer rights for workers".
