"It's concerning to see that level of debt clocked up without it being dealt with sooner," she said.
"Because that level of debt is going to be unmanageable for any of us let alone someone eligible for Kāinga Ora housing.
"People who are in public housing are already our most vulnerable, they live with limited resources to meet their needs and the needs of their families.
Green said it was a perplexing decision given that Kāinga Ora had put a halt on chasing debt during the pandemic.
"How is now chasing someone for $40,000 a responsible approach to a recognition on the impact of Covid-19 and the ability to pay rent?
"There's a difference between putting it on hold in terms of not holding it against them and delaying the time in which you take action, which is what's happened here."
Kāinga Ora oversees 65,000 homes and more than 200,000 tenants and its regional director for the Eastern North Island, Naomi Whitehead, said there were rare situations where it had to take customers to mediation.
"It is always our preference to work directly with customers to find a workable solution to any debt they may have and this approach is generally successful.
"While we do we engage in mediation with customers to address debt when required, it is only in rare situations where other tools have been unsuccessful that we would proceed to the Tenancy Tribunal."
Whitehead said the Covid-19 pandemic impacted many people's ability to pay rent and the ability for Kāinga Ora to work with its customers.
"As part of our response to Covid-19 we paused debt recovery activities, instead taking a welfare approach to support our customers through what were uncertain times," she said.