Police say 79 people are now dead or missing presumed dead after the fire at Grenfell Tower in west London.
Police Commander Stuart Cundy gave the new figure during a statement outside Scotland Yard on Monday, an increase from the previous number of 58.
"The new total may change as the investigation continues," Cundy said.
He said the search and recovery operation in the 24-storey Grenfell Tower continues, adding that it has been incredibly distressing for families.
"It's hard to describe the devastation the fire has caused," Cundy said, fighting back tears as he spoke.
He said it had been "incredibly emotional working in there ... On Saturday, I went in myself and went to the top floor."
Britain held a moment of silence for the victims on Monday, with emergency service workers bowing their heads in respect.
The fire ripped through the high-rise early last Wednesday. Cundy told reporters the "awful reality" was that it might not be possible to identify all the victims.
He said that authorities were continuing to investigate whether any crimes had been committed in the inferno.
Two British officials have said that new exterior cladding used in a renovation of Grenfell Tower may have been banned under UK building regulations.
Experts believe the new panelling, which contained insulation, helped spread the flames quickly up the outside of the public housing tower.
Some said they had never seen a building fire advance so quickly.
Trade Minister Greg Hands said Sunday the government is carrying out an "urgent inspection" of the roughly 2,500 similar tower blocks across Britain to assess their safety, while an opposition lawmaker urged the government to quickly secure documents in the Grenfell renovation for the criminal investigation.
Late Sunday, the Metropolitan Police released three photos from inside Grenfell Tower, which showed in close detail how the fire charred the building that once housed up to 600 people in 120 apartments.
Frustration has been mounting in recent days as information about those still missing in the blaze has been scanty and efforts to find temporary housing for the hundreds of now-homeless tower residents have faltered.
British Prime Minister Theresa May, criticised shortly after the blaze for failing to meet with victims, says the public inquiry looking into the tragedy will report directly to her.
The government also announced that those left homeless will be given at least STG5,500 ($A9,242) from an emergency fund.