A coalition composed mainly of relatives of missing and murdered Indigenous women is demanding the replacement of all remaining commissioners and a reset of the inquiry initiated by the federal Liberal government to look into the tragedy.

In an open letter sent to Prime Minister Justin Trudeau on Tuesday, about 150 First Nations leaders, activists and families of victims say they have been "deeply harmed by the inquiry's misguided processes." The letter is the third, and the strongest to date, written by family members and their supporters to express concern with the way the inquiry is being run. The number of signatories has increased each time.

The writers call upon Mr. Trudeau to do a "hard reset" and say "we are asking you to request the resignations of the existing commissioners in order to create the needed space to rebuild an inquiry that is Indigenous-led and community-driven."

Story continues below advertisement

Read more: Missing, murdered Indigenous women inquiry delays Thunder Bay hearing

A hard reset, the letter explains, does not mean restarting the inquiry from scratch. Rather, it says, all information collected to date would remain in place but the process would be rebuilt from the ground up with families of victims and communities at its centre.

Questions about the letter that were put to the Prime Minister's Office on Tuesday were redirected to Indigenous Affairs Minister Carolyn Bennett's office, who gave no indication that she is prepared to restart the inquiry with new commissioners.

"We remain committed to ending this ongoing national tragedy. The terms of reference are clear: Families should, and must, be at the centre of the commission's work," a spokesperson for the Minister said. "The commissioners have a plan and are dedicated to finding solutions to address families' concerns – this includes a constant process of learning and adapting as the inquiry progresses."

Inquiry spokespeople did not respond to requests for comment.

The letter writers say the commissioners have not taken the time to build good relations and the trust of victims' families and have repeatedly dismissed their concerns about being left out of the process. They accuse the commissioners of adopting a Western "colonial" structure for the inquiry, rather than one rooted in Indigenous traditions.

Marilyn Poitras, one of the five commissioners appointed last year, stepped down earlier this summer saying she could not perform her duties within the inquiry's current structure. A number of senior staff have also quit.

Story continues below advertisement

The most recent departure was that of Waneek Horn-Miller, the inquiry's director of community relations, who left on Tuesday. Ms. Horn-Miller is a former Olympian who is greatly respected by the First Nations community. An inquiry spokesperson said she left to spend more time with her young children.

Although a small group of families of missing and murdered women is advising the inquiry, the letter writers say the advisory group in no way represents the geographical and cultural diversity of all of those who have lost mothers, daughters, sisters, aunts and friends.

The inquiry was a campaign promise made by Mr. Trudeau after years of lobbying by Indigenous leaders and others. It was called shortly after his Liberal government took office in the fall of 2015 and officially began its work in September of last year.

Its mandate is to get at the root causes of why such a disproportionate number of Indigenous women in Canada meet violent ends. A 2014 report by the RCMP said the force identified nearly 1,200 Indigenous women and girls who disappeared or were slain in recent decades.

For many months, there have been complaints that the inquiry has failed to communicate with the families of victims and the public at large. Most of the testimony of family members, which was supposed to begin in the spring, has been delayed until fall and will come too late to be included in an interim report that is due in November.

"By hearing first from lawyers, many families and relations are unable to move forward in safety, even after health supports are now in place," the letter says. "In the absence of needed community supports and relationships with communities, too many voices continue to be missed by the approach of this inquiry."