The move follows the Government’s decision at the very end of last year to go out to consultation on a national plan to force developers to design in second staircases in all new housing blocks rising to around 10 storeys.

The Department for Levelling Up, Housing and Communities said the extra fire safety measure could cost developers around £1.6bn over a decade.

In a statement, the Greater London Authority planning department said: “The Mayor has consistently expressed concerns that the fire safety requirements in the national Building Regulations are not fit for purpose, so the proposed strengthened requirements and clear direction at the national level are strongly supported.

“This Government consultation envisages a very short transition period with new developments being encouraged to prepare for this change now.

“In light of this we are clear that, with immediate effect, all planning applications which involve residential buildings over 30m in height will need to be designed to provide two staircases before they are referred to us at Stage 2 for the Mayor’s decision.”

“We recognise that the earlier statement by the National Fire Chiefs Council referenced over 18m but, to be clear, our requirement for two staircases applies to residential buildings over 30m in line with the national position.”

The GLA’s Planning team said it was working with the city’s Boroughs to progress schemes now in the pipeline to ensure they include two staircases where necessary before any Stage 2 referral.

“We are all working hard to look at feasible options to secure this and try to meet key timescales, particularly given the impact planning delays may have on affordable housing grant funding.”