A 1,000-page document follows the first phase of an inquiry looking into the fire in west London on 14 June 2017, when 72 people were killed.
Fewer people would have died if the tower block had been evacuated sooner, the inquiry chairman concluded.
Sir Martin Moore-Bick’s full report will be published on Wednesday morning.
Parts of it were published early by the media following a leak to the Daily Telegraph.
Issues highlighted in the report included:
- A lack of training in how to “recognise the need for an evacuation or how to organise one”
- Incident commanders “of relatively junior rank” being unable to change strategy
- Control room officers lacking training on when to advise callers to evacuate
- An assumption that crews would reach callers, resulting in “assurances which were not well founded”
- Communication between the control room and those on the ground being “improvised, uncertain and prone to error”
- A lack of an organised way to share information within the control room, meaning officers had “no overall picture of the speed or pattern of fire spread”