The manufacturer of the combustible panels wrapped around Grenfell Tower has claimed other materials were responsible for spreading the fire that claimed 72 lives and said it could have been put out with a handheld fire extinguisher.

Arconic, which made the Reynobond aluminium composite panels which were filled with plastic that burned with an intensity that has been compared to petrol, made a combative closing statement, claiming that it was possible no one would have died if other aspects of the refurbishment had been different.

From next Friday, use of combustible ACM panels such as the Reynobond PE 55 material that was used on Grenfell Tower will be banned on residential and school buildings above 18 metres high. ACM panels were being stripped from 457 high-rise buildings across England, where they have been found to be in use. But Stephen Hockman QC, counsel for the US industrial firm, said it was “impossible to argue that ACM PE was non-compliant” with building regulations.

The performance of the uPVC windows in the fourth floor flat where the fire started, the synthetic insulation and other decorative cladding panels across the rest of the building were effectively responsible for spreading the fire, he said.

The fire rose 20 storeys in just 35 minutes to engulf the full height of the tower on 14 June 2017. The inquiry has heard expert evidence that the flames spread through the cladding system and had been fuelled by the highly combustible panels.

Arconic argued that the tragedy at Grenfell was not the result of its panels, but the combination of materials used in the 2016 £10m refurbishment, singling out the plastic window frames through which the fire was believed to have first spread from flat 16 into the cladding system.

Hockman told the inquiry chairman, Sir Martin-Moore Bick: “If the refurbishment of the interior window surrounds and the external envelope of the building had been carried out in a different way, it would have been possible for the firefighters to extinguish the fire in flat 16 before the fire even reached the cladding system.”

Referring to Behailu Kebede, the resident of flat 16, he claimed: “A simple fire extinguisher in his hands would have made a big difference to the outcome.”

Hockman said: “The external spread of flame was substantially exacerbated by combining ACM PE with combustible PIR [polyisocyanurate] insulation without any horizontal or vertical bands of non-combustible material to limit spread.

“The PIR insulation ensured the fire would spread to new portions of the building.”

He said this “meant that not only did the fire exit from the flat much more quickly than anyone would have expected, but it contributed to an increase in temp within the cladding system cavity.” If the insulation foam had been non-combustible, the London fire brigade might have been able to put it out, he said.

Arconic also argued that if internal features had been different, including fire doors, lack of sprinklers, the ventilation system, “then the fire would have penetrated the building much less rapidly and thus all or at least much of the tragic loss of life would have been spared”.

Hockman said: “The tragedy at Grenfell Tower shows the awful consequences which can arise when combustible materials are used in a particular combination. However, that does not show that the use of ACM panels in itself would have given rise to a risk to health and safety.”

Arconic made its case on the final day of phase one of the inquiry, after Moore-Bick had confirmed a major delay to the inquiry on Tuesday. The second phase of hearings, about the refurbishment, would not start until 2020 to give the inquiry time to examine at least 200,000 documents that were expected to be disclosed.

Moore-Bick added that the inquiry would move to larger premises in west London, following complaints from the bereaved, survivors and residents that the current venue in Holborn was too far away from their homes and that many of them had been unable to attend as a result.

Earlier in Wednesday’s hearing firefighters blamed the Royal Borough of Kensington and Chelsea for failing to make an evacuation plan for Grenfell Tower, despite expert advice taken before the disaster and legal obligations making clear it was necessary.

The Fire Brigades Union said that neither the council, which owned the 24-storey block, nor its tenants’ management organisation had any procedure for the general evacuation of the whole building and relied instead on the “stay put” strategy and leaving it to the fire brigade to devise an evacuation strategy if appropriate.

Martin Seward, counsel for the union, urged Moore-Bick to provide fire brigade staff with “protection from unwarranted criticism”.

Moore-Bick has faced widespread calls to conclude in his interim report – expected next spring – that the £10m refurbishment, using highly combustible cladding panels, was in breach of building regulations. But he has also heard conflicting evidence about whether the fire brigade should have tried to order a full evacuation before the building was engulfed in flames trapping and killing families and friends who huddled together in flats.

But the Kensington and Chelsea Tenants Management Organisation’s counsel, Alice Jarrett, said that although the building only had a single stairway “it managed to continue supporting evacuations and firefighting activities throughout the life of the fire” and that expert evidence suggested that 239 people could have got out after seven minutes.

She said the evidence from the survivors over the last six months had been “haunting” and “humbling” and said: “The inquiry will want to consider that the stairs at Grenfell Tower could have coped with a full building evacuation.”

The inquiry’s fire expert, Dr Barbara Lane, has said the stay put policy effectively failed at 1.23am, yet the London fire brigade kept the policy in place until 2.37am, when 107 people were still inside. Only 36 got out.

But the feasibility of an evacuation was rubbished by the Fire Officers Association. “Tragically it was never practicable to achieve a full evacuation of all residents from the tower within the window of opportunity for doing so,” it said in a statement. “We did not you let you down, the building let us all down.”