New Zealand’s lead agency supporting victims of crime and trauma has confirmed the terms of reference for an independent investigation into its workplace culture, confidence in leadership and workplace complaints processes.

The external review comes after reporting by RNZ of claims of a "toxic" and "bullying" workplace culture, four years after an investigation into similar allegations.

RNZ spoke to several current and former workers who raised concerns about the culture at Victim Support. One person described it as a "very unsafe environment".

The agency's chief executive, James McCulloch, earlier said the agency "does not accept that these claims reflect Victim Support today".

However, in a u-turn last month, Victim Support announced it had agreed to commission a review of the organisation's workplace culture, confidence in people leadership and the processes for resolving workplace concerns.

On Friday, Victim Support announced it had confirmed the terms of reference for the review.

"The Board commissioned the review to provide objective assurance on the organisation's current workplace culture, including assessing employee confidence in leadership, speaking-up processes and whether there are recurring or systemic issues that need to be addressed."

Every current employee would have the opportunity to participate in the review, Victim Support said.

The Board had appointed Charlotte Stevens as Independent Reviewer and Samantha Turner as Independent Peer Reviewer.

"The Independent Reviewer will select a random sample of employees from across different roles, functions, locations and lengths of service. Any employee who is not selected will also be able to request a confidential interview, make a written submission or participate through another mechanism established by the reviewer.

"Participation will be voluntary and confidential, and information will be anonymised and reported in themes."

The Independent Reviewer would determine the methodology and may seek further information or interviews where needed.

"The review will also consider employee survey results, workforce and exit data, previous independent reviews, organisational policies and other relevant evidence.

"The Independent Peer Reviewer will provide additional quality assurance. The Independent Reviewer will retain sole responsibility for the final findings and recommendations."

Board chair Rob Marshall said the terms of reference had been designed to give staff confidence in the process.

"The Board wants a clear, independent and evidence-based assessment of Victim Support's workplace today.

"We want our people to be able to participate openly and with confidence in the process. The Independent Reviewer will follow the evidence, identify what is working well and where improvements may be needed.

"We will take their findings and recommendations seriously - the wellbeing of our people and the quality of support we provide to victims are closely connected."

Victim Support said the review was focused on the agency's current workplace culture.

"Relevant historical information, including previous reviews, exit information and workforce data, will also be considered where it helps understand changes over time.

"The review is not an investigation into individual employment matters or allegations."

The final report was due in late November, when a detailed summary would be shared with staff, stakeholders and the public.