The London fire brigade’s readiness for the Grenfell Tower fire was “gravely inadequate” and fewer people would have died if it had been better prepared, a long-awaited public inquiry report into the disaster that killed 72 people has concluded.

The first phase of the report into the worst loss of life to fire in domestic premises since the second world war also ruled that the building had been refurbished in breach of safety regulations and that contrary to the evidence so far of the cladding panel manufacturer, Arconic, “the principal reason why the flames spread so rapidly up the building” was its aluminium composite panels and the “melting and dripping of burning polyethylene”.

The retired appeal court judge Sir Martin Moore-Bick, who led the inquiry, found that despite senior officers knowing about the risk of cladding fires from high rise blazes abroad, the “preparation and planning for a fire such as Grenfell” by the London fire brigade (LFB) fell far short of what should have been expected.

Moore-Bick used the 1,000-page report to criticise the LFB’s commissioner Dany Cotton for “remarkable insensitivity” for claiming in evidence to the inquiry that she wouldn’t change anything the brigade did on the night. It showed “the LFB is an institution at risk of not learning the lessons of the Grenfell Tower fire”.

He concluded many lives could have been saved if her officers had identified sooner that the fire was out of control and told residents to evacuate. He found that the LFB failed to train its incident commanders and firefighters in how to recognise the need for evacuation or in the dangers of combustible cladding.

Bereaved and survivors welcomed Moore-Bick’s much-delayed but “strong” conclusions after previously fearing he would delay making significant findings until the second phase of the inquiry which begins next year, which will examine the refurbishment project that preceded the fire.

Moore-Bick said there was already “compelling evidence that the external walls of the building failed to comply with requirements” of building regulations governing fire safety. They didn’t adequately resist the spread of fire, “on the contrary they actively promoted it” he said.

Lawyers for the LFB sought the ruling that the building breached regulations, arguing the £10m refit completed in 2016 was “catastrophically non-compliant with fire safety requirements”. The LFB has said the entire safety strategy for Grenfell Tower required any fire to remain compartmentalised and that it could not have been expected to cope if the building was changed to allow fire to spread as it did.

Moore-Bick praised the “extraordinary courage and selfless devotion to duty” of rank-and-file officers and said “those in the control room and those deployed on the incident ground responded with great courage and dedication in the most harrowing of circumstances”.

But the absence of an operational evacuation plan for Grenfell Tower was “a major omission” by the LFB, which was guilty of an “institutional failure” to inform firefighters about the risks of cladding fires before the disaster. On the night of the fire there was a “failure of command” which meant firefighters with extended-duration breathing kits were deployed too slowly.

Michael Dowden, the watch manager from North Kensington fire station and the commander on the scene for most of the first hour, was criticised for failing to consider an evacuation sooner and not making efforts to find out what residents were telling 999 operators or the conditions in the building. The inquiry heard an officer of his rank would not normally be in charge of such a huge fire, but Moore-Bick concluded: “I have little doubt that fewer people would have died if the order to evacuate had been given by 2am.”

The report was informed by evidence from hundreds of witnesses including 88 firefighters, control room officers and senior LFB commanders, together with 35 of the bereaved, survivors and residents.

In September, the LFB said leaders of the brigade have been interviewed under caution by Scotland Yard detectives in relation to health and safety offences.

The report is set to be published in full on Wednesday, but was circulated to the bereaved, survivors and residents on Monday morning. Those seen collecting printed copies included Nabil Choucair who lost six members of the family in the fire, Clarrie Mendy, the aunt of the celebrated young artist Khadija Saye who died with her mother Mary Mendy, and Natasha Elcock, the chairwoman of Grenfell United who escaped with her partner and daughter but lost her uncle, who lived on an upper floor.

Everyone who received an advance copy of the report was required to sign a non-disclosure agreement before taking it away.

Among the 72 victims of the fire were 19 children, and Cotton angered their relatives in her evidence when she compared preparing to tackle a fire like Grenfell to developing “a training package for a space shuttle landing on the Shard”, in other words something she would never need to do.

Moore-Bick addressed this saying it showed an “unwillingness to confront” the fact that in October 2016 LFB fire engineers produced a slideshow titled “Tall Building Facades” featuring cladding fires around the world. It warned of “a need to understand what products are being used in the facade system and their fire behaviour … These could affect the way fires develop and spread in a building.”

The findings came 26 months after Theresa May set up the inquiry in the wake of the disaster that devastated the north Kensington community and sparked a national fire safety crisis. Over 400 other tower blocks in England were found to have been wrapped in similar combustible cladding to that of Grenfell Tower.

Play Video 2:39 Grenfell Tower fire inquiry: powerful statements given by victims' families – video

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• This article was amended on 31 October 2019 because an earlier version mistakenly described Martin Moore-Bick as a retired high court judge. It was further amended on 7 November 2019 because an earlier version incorrectly referred to Grenfell as “the biggest single loss of life in London since the second world war”. It was worst loss of life to fire in domestic premises since that period.