The Grenfell Tower inquiry has cancelled its contract with KPMG over potential conflicts of interest.
The auditor has ties to the Rydon Group, which led renovations of the buildings several years ago, as well as ties to Celotex, which supplied Grenfell Tower's cladding.
"Following concerns expressed by some core participants, the inquiry team has discussed the contract with KPMG which has agreed that its work should now cease," a statement released by the inquiry said.
The decision follows the publication of an open letter sent to Theresa May urging the prime minister to reverse the decision to appoint the company.
A spokesman for the inquiry said KPMG had been appointed to provide "limited planning and programme management" during its "start-up phase".
"The company has had no role in the inquiry's investigations or decision-making processes and its contract contained strict confidentiality clauses to ensure that there could be no conflicts of interest," the statement said.
KPMG said it was confident there were no conflicts of interest between its work for the inquiry and its other clients, although the firm recognised that "strength of opinion about our role risks undermining confidence."
The signatories of the open letter, which included pop singer Lily Allen, politicians and academics, said they did not speak on behalf of Grenfell Tower victims, but were "deeply concerned over the obvious conflicts of interest" posed by KPMG's involvement in the inquiry.
The public inquiry into the fire, which killed 71 people, has been dogged by controversy since the appointment of retired judge Sir Martin Moore-Bick as its chairman.
Survivors and bereaved families have lobbied for an overhaul of the inquiry's shape due to lingering doubts about his suitability for the role.