"Management are reliant on the fact Pacific Islanders don't challenge authority even when decisions are poor. We are worried if we do there will be repercussions on us," he said.
"But as a collective, our perception is that we are being racially discriminated in the prison which is a breach of the Equal employment opportunities policy."
The staff member claimed management picked staff according to their ethnicity and physical size during the recruitment process and when assigning staff to roles.
"If you are an Islander you will probably go the high-risk units [B, C and D blocks] to de-escalate hostile and abusive situations. Most of the inmates in those units are Maori or Pacific Islanders.
"What we are saying is everyone should work there."
The guard added that some of his colleagues were now too scared to activate on-body cameras as they feared bosses might use footage against them; especially if the guards were caught in acts when trying to defend themselves.
The cameras, mounted on body armour, were introduced in 2015 after a successful trial at two prisons.
In the letter, the guard claimed that "for a number of years" Pacific Island staff were identified on appointment for placement by management "in the most hostile units".
"Hence we are subjected to more hostility and abuse from prisoners," it stated.
In response to the letter and comments from its author to the Herald on Sunday, Auckland Prison director Andy Langley said the prison had a policy of ensuring a balance of mix and gender at all units - including high-risk areas.
No ethnic group was targeted to work in high-risk areas.
This month the prison was planning a rotation exercise that "will focus on ensuring staff across the prison to have the opportunity to work across a range of areas and develop their skill sets".
"We need to ensure that we have the right balance and mix of gender, ethnic diversity and skills, particularly in high-risk areas to ensure that we are managing challenging and dangerous prisoners effectively and safely," Langley said.
The director said he was also in discussions with unions and staff networks about creating a serious assaults protocol that outlines the aftercare provided to staff assaulted at work.
"This is a protocol that was in place when I was a prison director at Manawatu Prison, to ensure that practical support is in place when staff members and their families need it most.
"The protocol is still in draft, and I'm looking forward to talking with staff about it further. We're also progressing a number of initiatives through the regionally developed Safer Auckland Prison plan, including additional intelligence staff; refresher integrity training and staff focus group sessions."
The letter was sent to Corrections HQ as guards support to three suspended colleagues who will appear in the North Shore District Court in relation to an alleged assault at Auckland Prison in late May.
One guard, aged 34, has been charged with causing grievous bodily harm with reckless disregard, and a second, 26, has been charged with assault with intent to injure.
A third man, aged 31, has been charged with attempting to pervert the course of justice.
