A costed proposal to fit Grenfell Tower with panels that did not burn was dropped amid pressure from the Conservative council to slash the cost of the refurbishment, the Guardian has been told.

A cladding company which fits nonflammable aluminium panels claimed it provided a £3.3m quote to fit its system to the 24-storey tower in west London at the request of Leadbitter, Kensington and Chelsea’s preferred contractor in 2013.

But a few months later the council decided Leadbitter wanted to spend too much on the refurbishment and put the contract out to tender to save £1.3m. It selected Rydon, which provided a lower price but fitted the building with combustible cladding which caught fire on 14 June 2017, killing 72 people in what lawyers for victims have called a “national atrocity”.

If the solid aluminium cladding had been chosen it would have almost certainly saved lives, fire safety experts said, and it could also have been cheaper. The council’s housing arm ended up agreeing to a budget which put the cost for the plastic-filled aluminium panels and synthetic insulation which burned so fiercely at £3.5m – £200,000 more than the quote for the noncombustible materials.

The survivors’ group Grenfell United described the development as heartbreaking. “It is more news that tells us our loved ones would be alive today if different decisions had been taken and if the people in charge had put safety first,” said Sandra Ruiz, who lost her niece in the fire.

“We need the inquiry to get to the bottom of why plans for the refurbishment were changed and why when the community raised concerns they were ignored.”

Peter Hillyard, the director of D+B Facades, said his company was asked to provide costs for solid aluminium sheets which do not spread flame, backed with mineral wool insulation which does not burn. He said the thought that his company’s safer and cheaper system was not used sent a shiver down his spine.

Geoff Wilkinson, an independent fire safety expert, said that if D+B’s version had been used it would have performed better in the fire.

“There would have been little or no fire spread, so the lives lost at Grenfell may have been prevented,” said Stephen Mackenzie, an independent fire safety consultant.

The emergence of the proposal will heighten scrutiny of the procurement decisions made by the Kensington and Chelsea Tenants Management Organisation (KCTMO), which managed the building, and the council, which owned it.

Scotland Yard detectives are investigating possible manslaughter and corporate manslaughter charges. They are also looking into “any failings of duty of care owed to victims of the fire”.

Downing Street indicated that the public inquiry, which starts on 21 May, would examine the claims. A spokesperson said: “It will be a decision for the public inquiry exactly what they choose to look at, but the prime minister has set out her view that the truth of what happened must be fully established.”

D+B’s system has passed the full-scale British Standard 8414 fire test, but Grenfell was clad in a combustible synthetic insulation faced with aluminium composite panels that had a combustible polyethylene core. The system has since been shown to fail the fire test.

Researchers claim the panel system used for Grenfell had a calorific value equivalent to 12,000 litres of petrol, while the insulation foam added the equivalent of almost another 20,000 litres. The foam has also been shown to release cyanide gas when it burns and it is feared this may have contributed to the death toll.

There was sustained pressure from the council to cut costs on the project despite the authority being in “robust” financial health, according to accounts for 2014. It had £235m in usable reserves and had underspent its budget for services by £23m.

The council had originally only wanted to spend £6m on Grenfell, but later set the budget at £9.7m when it realised it also needed to replace the heating system. In July 2013, however, the council’s housing committee reported that Leadbitter, which was interested in the nonflammable cladding, was on course to spend £11.3m and so it put the contract out to tender and launched a cost-cutting programme which it called “value engineering”.

The following summer, with Rydon on board, the council’s tenants management organisation emailed the project team: “We need good costs for Cllr Feilding-Mellen [deputy leader in charge of housing].” At that point £300,000 was removed from the cladding budget and zinc panels were replaced with the aluminium composite material with the plastic core.

At least 300 other tall buildings in England are clad in similar systems to Grenfell and need to be reclad after they failed fire safety tests. The system D+B proposed for Grenfell is now being used to replace the dangerous failed cladding on several of those towers.

A leaked report prepared for detectives has already claimed that the insulation on Grenfell “provided a medium for fire to spread up, across and within sections of the facade”. The Building Research Establishment found the fire would not have spread beyond the fourth floor flat where a fridge freezer had malfunctioned if the tower had not been clad in the combustible materials.

“Leadbitter sent us quantities as directed by Studio E Architects,” Hillyard said. “Based on quantities alone our budget was £3.3m. We provided figures based on our own ‘A1 non-combustible’ cladding system and our high quality composite windows. All went quiet and the next time we heard anything was in August 2013 when the tender notice was issued.

“Kensington and Chelsea were inviting main contractors to express interest under a ‘design and build’ contract. This was the last we heard and received no further requests from Rydon, who won the contract for the work.”

Sir Martin Moore-Bick, the chair of the Grenfell Tower inquiry which opens in full on 4 June, has said he wants to find out “what decisions about the exterior of the building … were made, by whom and when”. He also wants to know whether the cladding and insulation met building regulations and standards, who was responsible if they did not and “what factors or motives influenced the decisions”.



Bouygues, which now owns Leadbitter, declined to comment on the cost plan for noncombustible cladding, citing the police investigation and public inquiry.



Rydon, the council and KCTMO also declined to comment for the same reasons.