Bromley Council has approved the scheme despite strong objections from the London Fire Brigade, which said the decision to lower a residential block to 17.7m – just under the 18m threshold for requiring a second staircase – was ‘not ethically justified’.

Joint venture developers Hadley Property Group and Clarion Housing Group plan to build 230 homes across four blocks at the existing Blenheim Shopping Centre, which will be demolished to allow for the scheme.

Schematic of blocks in Penge scheme

One of the smaller blocks, a six-storey building of 26 flats known as block A, was reduced in height following changes to the ground-floor commercial ceiling height bringing it below the second staircase height threshold.

Two other taller blocks containing the majority of flats have been designed with second staircases.

The Fire Brigades Union and groups including Justice for Grenfell, End Our Cladding Scandal, Tower Blocks UK, and the Penge Preservation Society have signed a joint letter urging the Greater London Authority to halt the project until it meets the “highest standards of building safety”.

FBU general secretary Steve Wright said: “This is an attempt to cut corners and get around the building safety regulations introduced to avoid a repeat of the Grenfell Tower tragedy.

“If the development goes ahead in its current form, residents of this property will only have one staircase which they can use to evacuate. This could cost lives.

“It’s vital that Sadiq Khan uses his powers to block this attempt to circumvent the safety improvements that were introduced in the wake of the Grenfell fire.”

The LFB has submitted a nine-point objection to the plans on fire safety grounds, warning that the design poses a significant evacuation risk.

The letter has been sent to both Sadiq Khan and Bromley Council leader Colin Smith demanding immediate intervention.