The Grenfell Tower fire was fuelled by botched refurbishment decisions that went well beyond the use of flammable cladding panels and insulation, a report for the Metropolitan police has reportedly revealed.

Gaps around windows, wrongly fitted cavity barriers meant to stop fire, and dozens of missing or faulty door closers were also responsible for helping to spread rather than limit the fire that claimed 71 lives in June 2017, according to details that emerged on Monday.

A survivors’ group, Grenfell United, said the findings were shocking and showed “an industry that is broken”.

The analysis, seen by the Evening Standard, comes as the more than 530 core participants in the public inquiry digest a series of confidential technical reports commissioned by the inquiry chairman, Sir Martin Moore-Bick, parts of which, the Guardian understands, tell a similar story.

Those reports are expected to be made public when experts give evidence to the inquiry in June. Hearings start in earnest next month.

In parallel, Scotland Yard is investigating the blaze and has said it is considering possible manslaughter and corporate manslaughter charges.

The technical report for detectives has been drawn up by BRE Global, the building research company that runs fire testing in the UK. It reportedly identified multiple “deficiencies” in the £10m recladding of Grenfell Tower between 2014 and 2016, which was carried out on behalf of the Kensington and Chelsea Tenant Management Organisation, the social housing arm of the Royal Borough of Kensington and Chelsea.

Cavity barriers that are meant to expand and seal the gap between the concrete surface of the building and the cladding in the event of fire were of “insufficient size specification”, the Evening Standard reported the experts as concluding.

They were designed to close a 25mm gap but were installed with a 50mm gap. Some were installed upside down or back to front and the failures “provided a route for fire spread”.

There were gaps of 15cm between the window frames and concrete columns that were filled by a rubberised membrane, rigid foam insulation and uPVC lightweight plastic panels, the paper reported.

The report said that “none of the materials used would be capable of providing 30 minutes’ fire resistance” and this allowed “a direct route for fire spread around the window frame into the cavity of the facade … and from the facade back into flats”.

It meant the first obstacle the fire encountered as it escaped from flat 16 was the window frame, which provided “fuel” instead of a barrier. “The construction of the window did not provide any substantial barrier to fire taking hold on the facade outside,” BRE reportedly said.

The investigation, dated 31 January 2018, also found that almost half (45%) of the door closers on the 120 flats between the fourth and 24th storeys of the tower were missing or not working, which meant doors were left open when residents fled, spreading smoke and fire into the single stairway for escape.

It confirmed that the aluminium cladding panels and the insulation foam were combustible and noted that some of the insulation did not have a manufacturer’s logo on it.

Grenfell United said the findings were not surprising. “It was clear to us the refurbishment was shoddy and second rate,” the group said.

“We raised concerns time and time again. We were not just ignored but bullied to keep quiet. That a refurbishment could make our homes dangerous and unsafe shows that the contractors put profit before lives. It’s an industry that is broken. It’s also an industry that has been allowed to get away with this behaviour.

“Six people died in a fire at Lakanal House in 2009 and the government failed to act and make changes to regulations that would have stopped a fire like that happening again. Tonight we know people are going to sleep in homes with dangerous cladding on them. It is vital the police investigation and the public inquiry uncover everything that led to the fire and that the government now actually act so that this can never happen again.”

Scotland Yard and BRE Global are yet to comment on the report.

A spokesman for RBKC said: “We think the public inquiry and the police investigation are the right places for testing all the evidence as a whole. The council is clear – we have handed over thousands of documents – we are committed to finding the truth. We hope full disclosure of all the evidence, tested by the inquiry judge, will deliver the answers to ensure this never happens again.”