Cladding fitted to Grenfell Tower during its refurbishment was changed to a cheaper version, documents obtained by the BBC suggest.
Documents show the zinc cladding originally proposed was replaced with an aluminium type, which was less fire resistant, saving nearly £300,000.
The cladding is thought to have contributed to the spread of the fire that killed at least 80 people.
Kensington and Chelsea Council insists fire safety was not compromised.
Council leader to quit over fire response
Kensington and Chelsea Council leader Nick Paget-Brown has resigned following continued criticism of the council’s handling of the Grenfell Tower tragedy.
Mr Paget-Brown faced calls to resign from London Mayor Sadiq Khan and a number of other senior politicians.