London Mayor Sadiq Khan has said there are "questions that have to be answered" after residents of Grenfell Tower were told to stay in their flats in the event of a fire.
Mr Khan condemned the "bad advice" given to residents of the West London tower block that was engulfed in flames overnight, killing several inhabitants and leaving many trapped inside the burning building.
A newsletter to residents in 2014 said the "stay put" policy worked because the block had been designed according to “rigorous fire safety standards”.
"Thankfully residents didn't take that advice but fled... these are some of the questions that have to be answered," Mr Khan told BBC Radio 4.
"We have lots of people in London living in tower blocks... We can't have peoples lives being put at risk because of bad advice or lack of maintenance."
The newsletter, published by The Guardian, read: "Our longstanding ‘stay put’ policy stays in force until you are told otherwise. This means that (unless there is a fire in your flat or in the hallway outside your flat) you should stay inside your flat. This is because Grenfell was designed according to rigorous fire safety standards. Also, the new front doors for each flat can withstand a fire for up to 30 minutes, which gives plenty of time for the fire brigade to arrive."
Grenfell Tower residents' action group also published an image of "stay put" signs inside the block.
More than 50 people are being treated in five hospitals across the capital, London Ambulance Service said, as 200 firefighters continue to battle the flames that have decimated the 24-storey block.
Members of the action group warned in 2016 they believed the building posed a fire risk, and that "only a catastrophic event will expose" the potential for a "major disaster."
Following the fire, the group posted: "All our warnings fell on deaf ears and we predicted that a catastrophe like this was inevitable and just a matter of time."
Estate resident Ahmed Chellat said his family were safe after they were advised to stay in their 21st-floor flat with wet towels under the doors.
Mr Chellat's sister, brother-in-law, and their two children were advised to stay in the flat and that help was on its way, he told ITV.
He said: “It has been going on for quite some time regarding the safety of the tower. I live in the estate. The safety of the blocks has been a concern for a long time, not just now.”
Mr Khan said the incident was very "distressing".
Refurbishment had recently been carried out on the block with new cladding on the outside of the 1970s-era structure and work on the gas supply to the flats. It cost £8.7 million, and was completed in May last year.