The Grenfell Tower inquiry risks being a whitewash unless Theresa May installs a diverse panel to oversee proceedings, survivors and bereaved families have warned.
Those devastated by the disaster have launched a petition calling for the appointment of individuals from a wide range of backgrounds to sit alongside Sir Martin Moore-Bick.
It is said to be backed by families of around 50 victims, along with Grenfell United, an association of survivors from Grenfell Tower and nearby Grenfell Walk.
Currently, Sir Martin is heading the investigation into the blaze, which killed 71 people, supported by a legal team, civil servants and three assessors to advise on certain matters.
Misgivings about the retired Court of Appeal judge have persisted since his appointment in June, based on concern he lacked first-hand experience of the complex cultural factors underpinning the tragedy.
Grenfell Tower was a council-owned block which housed tenants from a range of social classes, religions and ethnicities.
Adel Chaoui lost four relatives in the blaze, his cousin Farah Hamdan, her husband Omar Belkadi and two of their daughters, Malak, eight, and Leena, six months.
He told the Press Association: "It's not about ethnicity. It's nothing to do with whether you're black, white, Arab, whatever - it is to do with experiences.
"(Sir Martin) is very, very good at what he does, but he does not necessarily understand us.
"At the same time, we are up against these industry bodies that are spending millions of pounds on legal resources that we are never going to get anywhere near.
"The only thing we have got is the reliance on a judge, supported by a panel that have a diversity of experience that will treat us impartially and fairly."
The petition urges the Prime Minister to use powers under the Inquiries Act 2005 to make the probe panel-led, or risk losing the support of families and residents.
Mr Chaoui said he and others would likely not attend the inquiry, which is due to begin evidence hearings next year, unless the format is overhauled.
He added: "I'm really hoping the Prime Minister sees all we're asking for is a fair crack at justice."
Sir Martin's decision to appoint three assessors with backgrounds in community work was seen by many as a concession to those concerned about his suitability.
But Karim Mussilhy, who lost his uncle Hesham Rahman in the fire, said: "No matter what the assessors recommend, it is up to him what he reports back to the Prime Minister - the fact that that gets left up to one person doesn't seem right, it doesn't give us any confidence."
Mr Rahman was only buried in recent weeks after a painstaking process to formally identify his body, which was recovered from the 23rd floor.
Inquests have been opened and adjourned into all those killed in the June 14 inferno, with Westminster Coroner Fiona Wilcox last week expressing confidence the death toll would not rise.
Mr Mussilhy continued: "In the beginning we didn't know anything about my uncle or his outcome for two and a half months...it was just a time of limbo, we were stuck in this big, black, dark space, waiting for any news.
"Then after that it's just pure determination - I lost my uncle, I know friends that have lost many others - and it is just wrong, we will not allow their deaths to be for nothing.
"We want to make sure this never happens and they are never forgotten."
The move came as the Home Office again extended the deadline to apply for an immigration amnesty offering undocumented residents of Grenfell Tower temporary protection from deportation.
It is believed that those living in the building illegally may not have made themselves known to authorities out of fear of reprisal.
Such residents now have until January 31 2018 to sign up to the scheme, which gives them 12 months leave to remain in the UK that is eligible for extension.
After five years, this can be turned into permanent residence subject to security, criminality and fraud checks, the Home Office previously announced.
Immigration minister Brandon Lewis said on Thursday that rules had also been slackened, allowing undocumented migrants from the tower to switch their method of applying for immigration and no longer compelling them to provide certain information.
The petition can be found at https://petition.parliament.uk/petitions/206722