Nurses at Auckland's Starship Children's Hospital say this is the worst nursing shortage they've seen, as cancer treatments are delayed.
On Thursday, Health Minister Simeon Brown confirmed some treatments were delayed up to seven days.
Earlier that morning, Health New Zealand's Starship Hospital director Dr Greg Williams said the paediatric haematology/oncology service has had to reschedule some treatments due to a shortage of nurses.
"These decisions are not made lightly and are based on clinical need," he said, adding: "Starship is recruiting experienced and new graduate nurses as quickly as possible".
But two nurses who spoke to RNZ on the condition of anonymity, said staffing had been a critical issue for over a year.
They said there was a lack of experienced staff as nurses needed to complete a certain amount of qualifications, hours and training to be competent in chemotherapies, high-risk therapies and monitoring.
"We're getting a lot of new graduates - which is brilliant - but we need the staff to support them.
"We want to keep our new nurses not scare them away.
"It doesn't really help with our workload, at the moment they can't give chemotherapy or those high-risk therapies, so we still have to do them, as well as train the new nurses.
"It's not just the amount of nurses that we're employing, its the experience we need them to have - there's no point of employing seven new grads."
The nurses said new graduates only got two or three weeks working with another more experienced nurse and observing, before they were "on their own on the floor" in a children's oncology ward.
"It's intense, it's emotional and it's a really high-risk area. I just don't think two to three weeks is enough and we're not giving them enough support that they need to keep our staff and staff retention is really important for our kids."
A spokesperson for Brown earlier told RNZ vacancies at Health NZ were the result of natural attrition such as parental leave and retirement, but the nurses disagreed.
"That is absolutely not the case."
They said some nurses left because they felt unsupported.
One thing the nurses did want to make clear to parents and the general public was patients would still receive support and care they needed.
"We will do everything we can to make sure we get those children seen and safely cared for," they said.
"The tricky thing is we're doing that at the detriment of our nurses.
"We want to reassure parents out there that their children will get the care and the treatment they need, the children are safe."
Following media reports in recent days, the nurses said many parents on the ward were stressed, worrying their children wouldn't get the care they needed.
"We want to reassure them all - and that is what we've spent most of the day doing... their kids will get the treatment that they need."
They said they wanted to thank the parents for messages of support they had received.
The nurses said however, they were not currently able to spend the time really getting to know families like they used to, or spend time with the children and play with them.
"We purely come in now to do the treatment... and just get through the shift safely."
The bottom line, they said, was they needed more experienced nurses.
"This is not a cry for money, we are not asking for another pay rise, we're crying out for more staff - and more staff who can train up our new starters."
They encouraged Brown to come to the hospital and meet with staff, to see what it was like in person.
"We'd be interested to speak to him if he's keen to, come and have a meeting with us, we'd be happy to have conversation."
They said Brown had not been to visit them in person before.
Brown and Health NZ have been approached by RNZ for comment.
On Thursday, a spokesperson for the minister said all children at Starship Hospital were still being treated, though a handful of chemotherapy sessions have been delayed for a few days - but no more than seven.
Two bone marrow transplants were moved "slightly", but both were still going ahead.
Williams said the oncology departments are being supported by staff in other parts of Starship and Auckland City Hospital.
Health NZ said Starship's cancer ward was three months away from being fully staffed.
