Fire chiefs have said it is “imperative” that an inquiry establishes why Grenfell Tower came to be covered in dangerous flammable cladding.

The hearings into the disaster which killed 72 people in 2017 will reopen on Monday, after being halted in March due to the coronavirus pandemic.

Attendance will be limited to comply with social distancing guidelines, with only members of the panel, counsel to the inquiry, the witness giving evidence and their legal representative, as well as support staff and an invited journalist allowed to attend.

Ahead of the restart, Roy Wilsher, head of the National Fire Chiefs Council (NFCC) said: “It is imperative we find out why a non-compliant, extremely dangerous cladding system was on Grenfell Tower, along with hundreds of other buildings across the country.

“The bereaved, survivors and families deserve answers and I truly hope they get the answers they need from Phase 2.”

During the break in hearings, a Parliamentary committee warned fixing all serious fire safety defects in high-risk residential buildings could cost up to £15 billion.

Some 2,000 residential buildings are still wrapped in dangerous cladding, with thousands of homeowners sleeping in potential fire traps every night, according to the report by the Housing, Communities and Local Government Committee (HCLGC).

Also in the weeks since the Inquiry last sat, a pledge from the Attorney General promised that oral evidence given on behalf of companies to the Grenfell Tower Inquiry cannot be used in any future prosecution over the blaze.

Protections for anything said by individuals to the public inquiry were guaranteed in February, but in June Suella Braverman QC extended this to cover “legal persons” or companies.

It means people who cannot be separated from their firms, including senior directors, executives and sole traders, cannot refuse to answer questions by claiming the legal right of privilege against self-incrimination.

Ms Braverman said in a statement: “The bereaved, survivors and their relatives have been very much in my mind in making my decision and I hope that the extension to the undertaking helps them to find the truth about the circumstances of the fire.

“It is important to know that I am granting the extension in the knowledge that it will not jeopardise any future criminal investigation or prosecution and that it does not offer anyone immunity from prosecution.”

Matt Wrack, general secretary of the Fire Brigades Union, said: “The bereaved, survivors and residents of Grenfell should have seen justice delivered by now, but instead have been forced to wait – first because of the obscene moves from corporate witnesses to secure immunity from prosecution, and then because of the coronavirus pandemic which made continuing the inquiry all but impossible.

“We are now more than three years on from the disastrous fire at Grenfell Tower and there can be no more painstaking postponements.

“Before hearings were paused, we saw those involved in the refurbishment of Grenfell Tower try again and again to evade responsibility. But in the cold hard light of day, the crimes of those who wrapped the building in flammable cladding, and who ignored the concerns are residents, are apparent – and they must be held accountable.”