His comments come after two reports into unannounced inspections at Christchurch Men's Prison in February 2020 and Whanganui Prison last September.
"It is disappointing that both inspections showed a high number of recommendations I made during my previous visits had either not been achieved at all or only partially achieved," Boshier said.
Boshier has described the two prisons as undignified and barren, and the pace of progress by the Corrections department as "glacial".
"The apparent inertia that seems to afflict Corrections in implementing change adds to my frustration at the glacial pace of progress in improving conditions and treatment for prisoners and undermines public confidence in the department."
In his inspection of Christchurch Men's Prison last year, the Chief Ombudsman found that of the 54 recommendations made in 2017, 27 had not been achieved and only 12 partially achieved.
Boshier remained concerned about the prevalence of the use of force in the prison's Intensive Supervision Unit.
"My inspectors observed footage where multiple staff used force on vulnerable prisoners to gain compliance, despite little risk to staff or the prisoner being evident."
He made 26 repeat recommendations and one new recommendation around the general treatment and conditions of prisoners, following his 2020 inspection.
In relation to Whanganui Prison, of the 35 recommendations made following an inspection in 2018, inspectors found in September last year that 20 had not been achieved or only partially achieved.
"Of particular concern is that among my recommendations to Whanganui Prison in 2018 was that staff awareness of LGBTQI+ issues was raised. Although Corrections has developed a strategy and training to address this, I consider more work and awareness of LGBTQI+ issues is needed.
"Derogatory language was used by some staff when speaking to my inspectors in relation to a transgender detainee. Misgendering, deadnaming and any other forms of dehumanising and derogatory language in relation to transgender people is unacceptable."
Boshier also highlighted the use of "dry cells" as alternative accommodation for at-risk prisoners as a practice that should be halted immediately.
"Dry cells are a desolate and barren environment for prisoners who are already vulnerable. I do not consider it is ever appropriate to put at-risk individuals into cells that have no toilets and no drinking water."
Boshier said there had been some improvements however, including a reduction in double-bunking at Whanganui Prison and improved interaction between prisoners and staff at Christchurch Men's Prison.
- RNZ