A door from Grenfell Tower could only hold back a fire for half the time it had been designed to, a police investigation has found.
Experts said the flat door was supposed to resist fire for 30 minutes, but only lasted 15 minutes.
The test was part of the Met Police investigation into the fire in west London on 14 June which killed 71 people.
Kensington and Chelsea Council said the test results are “inconclusive”.
Natasha Elcock, a survivor from the tower and a representative of the bereaved and survivors’ group Grenfell United, said it is “time people lives are taken more seriously and that includes everyone from every walk of life”.
She added: “It’s shocking – first the cladding and insulation, then the doors. Who knows what else is putting people’s lives at risk?
“The government should have improved regulations after previous fires. We can’t listen to any more excuses.
“Nothing can bring our loved ones back but we must make sure a fire like this never happens again.”
It is believed Manse Masterdor was the manufacturer of Grenfell Tower’s fire doors, which were installed between 2011 and 2012.
Since then, the company’s trade and operating assets were taken over by Synseal – which continues to trade under the name Masterdor.
On Thursday, Synseal said that the products in question were no longer being sold.
A Kensington and Chelsea Council spokesman confirmed three doors were tested and provided “less protection than guidelines recommend”, but said test results are “as yet inconclusive”.
He added that the government must give “clear advice” so that residents across the country can understand any safety implications.
“We understand this news will be of particular concern to residents in this borough, which is why we are urging the government to move as quickly as it can to give us clarity,” he said.
The Ministry of Housing, Communities and Local Government said Housing Secretary Sajid Javid is due to make a statement on the subject in Parliament later this morning.
In a letter sent to families who live in the tower, Matt Bonner, a senior investigating officer from the Met Police, said: “Independent experts have advised that the risk to public safety is low, and that evidence from the suspected issue does not change this assessment.”
The force said the forensic examination and testing phase is ongoing so it did not want to comment on the potential impact “any test result may have on the overall criminal investigation”.
The information has been given to the Ministry of Housing, Communities and Local Government “so that they are able to take any action required”, the Met added.
A second procedural hearing of the Grenfell Tower Inquiry, chaired by Sir Martin Moore-Bick, will take place on 21 and 22 March to review its progress.