The problem-plagued inquiry into murdered and missing Indigenous women and girls has lost another key staffer as dozens of family members, activists and academics have written an open letter to Prime Minister Justin Trudeau demanding the "deeply misguided" inquiry get a hard reset.

CBC has confirmed Waneek Horn-Miller, who was the director of community engagement, is leaving the inquiry to focus on her family.

At the time of her appointment in February, the Mohawk former Olympian, media personality and health advocate called the job a "mission."

Waneek Horn-Miller has stepped down as the director of community engagement for the MMIWG. (Submitted by Waneek Horn-Miller)

The development comes as the letter from the coalition says relatives have been shut out of the process and that commissioners are on a path that will not lead to the successful fulfillment of the inquiry's mandate.

"They have continually dismissed our concerns, refused to take steps to rebuild trust, and have maintained a deeply misguided approach that imposes a harmful, colonial process on us," the letter reads. "This has and continues to create trauma as well as insecurity and a lack of safety for our families, communities, and loved ones."

Families wrote a letter complaining about being excluded three months ago, but say their deep-seated concerns were ignored. The letter was used only to pit families against families, the coalition said.

Families and supporters are also accusing Indigenous and Northern Affairs Minister Carolyn Bennett of dismissing their concerns.

A statement from the minister's office said the government remains committed to ending the "ongoing national tragedy," and that the inquiry's terms of reference require that families be central to the commission's work.

After meeting with the commissioners, Bennett was satisfied they had a plan and dedication to address families' concerns, which will adapt as the inquiry progresses.

'Immediate action'

The statement said the government is working in the meantime with Inuit, First Nations and Métis partners to honour the lost and to advance reconciliation.

"We've taken immediate action with a new gender-based violence strategy, changes to the child and family welfare system for Indigenous children, safe housing, shelters and work with British Columbia towards safe transport on the Highway of Tears," the statement reads.

The inquiry has been plagued with problems, including staff departures and last month's resignation by Marilyn Poitras, a Métis professor at the University of Saskatchewan. She cited issues with the "current structure" of the inquiry, which is set to get underway this fall.

Some of the missing and murdered Indigenous women and girls. (CBC)

But the letter from relatives and supporters says too much damage has been done and too much time has lapsed to rebuild trust now.

Instead of drawing on Indigenous knowledge and practices, the inquiry has been rooted in a colonial model that prioritizes a Eurocentric medical and legal framework, it reads.

"Such an approach is rooted in a broader culture of colonial violence that is inherently exploitative towards Indigenous peoples and causes ongoing trauma and violence for us as families," the letter says.

Health, legal and community relations team workers for the inquiry are scheduled to be in two Saskatchewan cities this week to meet with families who wish to participate.

The teams are in Regina and Saskatoon to get in contact with families who want to participate in the truth gathering process which will be held in Saskatoon in November.