A teenage cancer patient's mother says unmasked Mongrel Mob members in Christchurch Hospital's intensive care unit put her son at risk.
Anne-Maree Thomas said she felt no one was willing to ask the gang members to put on a mask.
It happened during the same two week period leading up to Christmas when RNZ reported the gang members blocked off public hospital carparks.
Te Whatu Ora Waitaha said current hospital policy required all visitors to wear a medical paper face mask.
Thomas relocated to Christchurch in July last year for her son's cancer treatment. He was in the intensive care unit (ICU) after undergoing a 15-hour operation in December when she first noticed the gang presence.
"There were other people in ICU, or waiting in the waiting room, that happened to be, not known to me at the time, Mongrel Mob, mostly women... Quite a few of them, no masks on," Thomas said.
"And then slowly after that, the next few days, it just got bigger and bigger, lots of Mongrel Mob there."
The problem was not the presence of the members, but their failure to wear masks, Thomas said.
"All the people in ICU at the time, and in the children's high care unit next door, are the [patients] that are just really, really ill. If they were to get an infection through [ICU], you'd probably wipe out half of them."
Thomas became concerned for her son's health as the number of gang members grew.
"They took over the carparks at the hospital, they took over the waiting rooms. They took over the whānau room, but they got kicked out of there.
"But nobody did anything. I rang the hospital twice, I rang the police three times, I even rang the police on 111," she explained.
Police said the call taker spoke with the Christchurch Hospital ICU charge nurse during the first call.
The nurse told police security at the hospital were aware of the gang presence, and there were no issues that required police attendance.
Thomas said police also asked if anyone was armed.
"I said: 'Really? You're telling me you want me to find out whether the Mongrel Mob is armed?' ... what a joke. I said it's not about that, this is about protecting people up there [in ICU]."
In a statement, police said it was usual practice to ask someone reporting an incident if anyone present had been seen with a firearm. It could be one of a series of questions asked to gauge risk.
In this particular case, police said: "There were no specific reports of any aggressive or threatening behaviour that would require an emergency response."
"Police prioritise calls for services based on immediate risk to life, safety and property, along with the availability of staff in the wider area. At times this means staff may not attend to issue an infringement," the statement said.
"Failing to wear a mask in a hospital setting is an infringement offence. Anyone who fails to comply with the face covering rules can be fined.
"However, police take a graduated response to any situation and first aim to engage, educate, encourage and then enforce."
Police also confirmed no officers attended Christchurch Hospital in December to address unmasked gang members.
In a statement, Te Whatu Ora Waitaha said staff reminded visitors to wear a mask.
"Our security team are also available to assist if necessary and those refusing to wear a mask are asked to leave. Police may be asked to attend the hospital ... if required," it read.
Te Whatu Ora Waitaha said it was unable to comment further for privacy reasons.