Anything said by witnesses to the Grenfell Tower inquiry will not be used to prosecute them over the fire, the Attorney General has said.
The second phase of the inquiry has been on hold for several weeks, as many witnesses threatened to stay silent without a guarantee.
The request came from lawyers representing those who were involved in refurbishing the block before the fire.
It does not mean companies or individuals cannot be prosecuted.
The chairman of the inquiry backed the request earlier this month but had needed approval from the Attorney General.
Suella Braverman’s office said she had concluded the guarantee was needed to “enable the inquiry to continue to hear vital evidence about the circumstances and causes of the fire”.
Without it, she concluded that some witnesses would be likely to decline to give evidence, her office added, by claiming the legal right of privilege against self-incrimination.
The second phase of the inquiry, which began in January, is looking at how the building came to be covered in flammable cladding during its refurbishment between 2012 and 2016.
In a statement, Ms Braverman said: “The undertaking I am providing to the inquiry means it can continue to take evidence from witnesses who otherwise would likely refuse to answer questions.
“These questions are important to finding out the truth about the circumstances of the fire. The undertaking will not jeopardise the police investigation or prospects of a future criminal prosecution.”
Inquiry chairman Sir Martin Moore-Bick said he sought the pledge to allow individual witnesses to provide the public hearings with a truthful account without fear for the future, allowing him to make recommendations based on the fullest body of evidence possible.
The proposed undertaking will cover oral evidence from individual witnesses only.
Evidence given to the inquiry in written statements or documents can be used against them in any future prosecution, the Attorney General’s Office said.
Sir Martin said the Metropolitan Police Service did not suggest that granting the undertaking would “hamper” their concurrent investigations.
Scotland Yard is carrying out its own investigation into possible crimes ranging from gross negligence manslaughter and corporate manslaughter to health and safety offences over the 2017 fire which killed 72 people.
The application for protections related to witnesses from firms including external wall subcontractor Harley Facades, main contractor Rydon, architects Studio E, and window and cladding fitters Osborne Berry.
The second stage of the inquiry previously heard that the main designers and contractors involved in the refurbishment appeared to predict that the cladding system would fail in a fire, up to two years before the disaster.
The inquiry’s first phase found the cladding was the “principal” reason for the rapid and “profoundly shocking” spread of the fire at the 25-storey building.