An architect has criticised plans to change windows at a “unique” tower block designed by a pioneer of modern architecture.
John Allan warned plans to raise the height of horizontal bars known as transoms for windows at Sivill House in Colombia Road, Bethnal Green, would not be looked on kindly by future generations if "key architectural values" are "lost".
The 19-storey housing block was opened in 1966 and designed by firm Skinner, Bailey & Lubetkin.
In the 1950s, Soviet émigré, Berthold Lubetkin - known for Highpoint apartments, Finsbury Health Centre and London Zoo's Penguin Pool - undertook the Dorset Estate social housing project of which Sivill House is a part.
Mr Allan said: "Sivill House is unique in Lubetkin's oeuvre, being the only standalone 'skyscraper' he ever designed.
"It presents a highly distinctive and illuminating account of his architectural philosophy. Tower Hamlets should be very proud to have this in their territory and this refurbishment project should be approached with exactly the same degree of conscientiousness as would be expected in the conservation of any other designated heritage asset."
Mr Allan, who knew Lubetkin personally, has written to the government urging it to list the block at Grade II or II* "as a matter of urgency" due to the works due to be decided on by Tower Hamlets Council.
The Twentieth Century Society has warned it will object to the plans unless the proposals are changed to keep the original windows' proportions.
But the council's housing management firm Tower Hamlets Homes (THH) - which oversees Sivill House - says the plans "keep as close as possible" to the original window designs.
A THH spokeswoman said: "We are carrying out major repair work at Sivill House to ensure the blocks comply with current building regulations and so that the safety of residents is maintained.
"The specification for the work is to replace windows on a 'like for like' basis and the windows have been designed taking into consideration the building regulations."
Sivill House neighbours argue child locks would be enough to make the windows safe, but the THH spokeswoman said this wouldn't be enough to satisfy current legislation.
A spokesman for residents' group, The Sivill House Steering Group, said: "We are determined to protect this unique design and its historical importance."
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