Homeowners in two tower blocks in Limehouse have been told they will need to foot an estimated £2 million bill after engineers said their flats might not survive a large explosion.
Leaseholders in Brewster and Malting House face paying between £55,000 and £77,000 each to improve the "structural integrity" of their properties.
Residents will also have to leave their flats for a period while the work is completed over 18 months.
Tower Hamlets Council said the problems were found after flammable cladding was stripped from the buildings and replaced last year.
Interior designer Belinda Lemesuriek, 39, lives in a one-bed in Brewster and has been told she will owe £55,000.
She said: "It is scary and stressful and will make people homeless."
The council admitted an explosion was unlikely as the towers do not contain "piped gas". They have offered to buy back about 32 leasehold flats.
Miss Lemesuriek added: "Even if we were to sell our flats… it seems they would not pay nearly enough for us to buy another property in the area."
The blocks were built as council housing in the Sixties and contain 112 flats.
In 2018 non-aluminium cladding was replaced after failing fire safety tests and the cost was covered by council and government funding. At the same time the council completed a structural review.
Private engineers Wilde Carter Clack found the blocks required "intrusive structural strengthening, particularly as the buildings were at risk of progressive structural collapse in the event of an explosion and possibly following an extremely intense fire, which could cause floors to buckle". The buildings are not at risk of collapse otherwise.
Mavis Hawkey, 80, who lives in Brewster House, said: "We had assumed these were more safety works and would be funded. I'm not sure why they are not. The enormous cost has caused a great deal of stress and anxiety. I'm 80 years old and struggling to cope with this situation."
The council is planning to further consult leaseholders on the works.
Mayor John Biggs said: "This is a deeply stressful and worrying situation for all involved, particularly for leaseholders, so it is right that we look again at all of the options to ensure we take the best course of action. Council officers will be speaking again with residents in Malting and Brewster to better understand their views ahead of any final decision."
Leaseholders in council properties are protected from huge bills by "Florrie's Law" — named after Florence Bourne, 93, who died after being unable to pay £50,000 for the refurbishment of her block in Newham in 2013.
The government then capped the amount local authority leaseholders have to pay for repairs at £15,000. However, it only applies if works are partly funded by a central government grant. If not, the council can pass on the entire cost.
Ms Lemesuriek said: "We pay service charges and building insurance but it seems this doesn't cover these repairs. Asking us for tens of thousands pounds out of the blue is unfair. No one would ever expect to have a bill this large dropped on them."
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