The fire brigade has raised fears over the safety of a planned north London flat block with an EV bus depot in the basement.
Proposals for the Broadwalk shopping centre and nearby area in Edgware include building more than 3,300 homes, and relocating the existing Transport for London (TfL) bus station.
The London Fire Brigade has warned that the structure of a flat block housing the bus depot could be at risk if there was a fire.
There would be two tower blocks up to 29 storeys high, a hotel, supermarket, cinema and other shops along.
The Deans Brook Nature Reserve would also receive a facelift.
Ballymore said the current TfL bus garage would be relocated and the new basement garage underneath several blocks would initially be designed to house regular buses.
They would later convert this to house EV buses if given permission by Barnet Council.
There have been almost 2,000 public objections since Ballymore submitted an outline planning application in July.
The LFB raised issues over the potential "structural collapse to the blocks of flats" above the garage if there was a fire and said the current application should be considered as a whole.
It said: "The structural integrity of many of the blocks above the bus garage are intrinsically dependent on the structural integrity of the bus garage below.
"The potential for so many EV buses poses risks that are not fully understood by the industry at this point in time."
The concerns were flagged after a series of fires involving electric buses in London.
The letter said the provision of only one lift for firefights and an access road which can bear only up to 12.5 tonnes, which could not take firefighting vehicles, was insufficient.
LFB also warned of "an incident involving an EV emitting a toxic vapour and the potential for a vapour cloud explosion if that cloud is confined".
A spokesperson for LFB said: "Despite not being a statutory consultee on such planning applications, we would always look to provide a response around the fire strategy in high-rise buildings, particularly where it also involves an emerging fire hazard such as electric vehicles.
"While further detailed plans are expected to be submitted over time, we have highlighted safety issues in our response and we strongly recommend that a development of this scale should be supported by a comprehensive, site-wide fire strategy report."
Anuta Zack, from Save Our Edgware, described the scheme as "a ticking time bomb that we refuse to live with".
A spokesperson on behalf of the development said Ballymore welcomed LFB's response "as an essential part of the development’s ongoing consultation process".
The company said it remained "in ongoing dialogue" with the brigade.
The transition to electric vehicles was a "vital part of delivering electric buses across the capital", the spokesperson said.
They added: "The garage will not be operational until 2030 at the earliest and we remain clear that no electric vehicles will be permitted unless and until the design has been approved by the London Fire Brigade, Barnet Council, the Health & Safety Executive and Building Control.”
