Permission to build a 51-storey skyscraper with a single fire escape for more than 400 flats is expected to be granted on Thursday, in a move safety campaigners described as “scary”. Plans for one of the UK’s tallest residential buildings will go before the London Borough of Tower Hamlets planning committee on Thursday evening with a recommendation from officials for approval. The Cuba Street tower, close to Canary Wharf, will have 655 bedrooms, with the highest close to 170 metres in the air – two-and-a-half times the height of Grenfell Tower. It features only a single staircase, which is allowed under building regulations if the strategy in a fire is to tell residents to stay put in their homes. All new apartment blocks above 11 metres must also be fitted with sprinklers. But fire safety experts warn it is inadequate because design features meant to keep people safe in their flats might fail, triggering an evacuation while firefighters are trying to use the same stairs in the opposite direction. The tower is being developed by Ballymore, and residents of another of the company’s nearby apartment complexes, New Providence Wharf (NPW), have also raised concerns about the design. Smoke clogged corridors at NPW during a serious fire in May, which injured three people. The London fire brigade discovered ventilation systems, the firefighter lift and door holders didn’t perform as expected. “It’s very scary,” said Natalie Carter, a resident at New Providence Wharf and part of the Tower Hamlets Justice for Leaseholders group. “If they do need to evacuate for any reason you are talking about doing that on the same staircase the firefighters would be using, it just seems absolutely bonkers.” Arnold Tarling, a chartered surveyor and fire safety expert, added: “It is utter madness that this is still allowed.” He recently inspected a newly built apartment tower in the same area of London and discovered serious failings that would mean residents might not be safe to stay in their flats in a fire. He said the worst-case scenario of having a single staircase was “another Bronx fire, another Grenfell, another Lakanal type fire”, references to blazes in social housing blocks last week in New York, in west London in 2017 and in south London in 2009 that together killed 89 people. Fire safety experts contacted by the Guardian said that second staircases reduce the area for saleable apartments and so limit profitability. The president of the Royal Institute of British Architects, Simon Allford, said public safety must be the fundamental concern of the government’s new building safety regulator. He called on it to set a new height threshold at which at least two staircases are required to provide for access for firefighters and residents’ evacuation. The international building code, which is adopted by many countries and US states but not the UK, requires that buildings over 128 metres have at least two staircases. The latest 2019 version of UK guidance states simply that “appropriate means of escape in case of fire from the building … [must be] capable of being safely and effectively used at all material times”. “In my opinion you have to build in resilience,” said Russ Timpson, secretary of the Tall Building Fire Safety Network. “You have to have a plan A and a plan B because if stay-put doesn’t work, a simultaneous evacuation is an almost impossible challenge with a single staircase. Around the world firefighters talk about having one escape stair and one attack stair.” Asked about the single staircase, a Ballymore spokesperson said the project “will only move forward with the support of the London fire brigade and building control”. The Department for Levelling Up, Housing and Communities said it is “reviewing the building regulations guidance, including what provision of escape routes is needed to ensure residents are safe in the event of a fire”. A spokesperson said: “We’re bringing in the biggest improvements to building safety in 40 years – with tougher regulations that will give more rights and protections for residents and make homes safer.” Building safety campaigners are also arguing Ballymore should invest first in fixing fire safety problems in existing blocks as part of the wider building safety crisis. On Monday, Michael Gove, the secretary of state for levelling up, housing and communities, announced the government would legislate to force developers to pay to fix unsafe apartment blocks. The Treasury told Gove he “must prioritise safety over supply”. Ballymore said it has “committed significant investment towards covering the cost of cladding remediation, with works having been under way across our developments for some time, and are working to ensure leaseholders bear no cost”.