The Twentieth Century Society fear mosaics created by Sir Eduardo Paolozzi will be lost at Tottenham Court Road station.
The society said the archways of "very high quality" mosaics should be saved.
Redevelopment work is intended to improve access with new entrances and lifts.
Transport for London (TfL) said efforts had been made to retain over 95% of the Paolozzi mosaics in their current position or with a mixture of new and original tiles, but for structural reasons the mosaic covered arches could not be saved.
Henrietta Billings, senior conservation adviser at the Twentieth Century Society, warned that mosaic covered arches over escalators and a large decorative panel would be "demolished imminently".
She added: "But both of these pieces are of very high quality and we believe they could be successfully retained within the new station - or relocated.
"To destroy them would be a tragic loss and London deserves better."
Gareth Powell, director of strategy and service development at LU, said the Paolozzi Foundation had been involved in efforts to ensure the station continues "to provide a home for the work".
Mosaics have been restored and replaced on the Northern Line and similar work will be carried out on the Central Line.
He added: "This process involved colour matching and following the same production used for the original tiles.
"We also have plans to relocate the signature pieces at the former Oxford Street entrance."
Mosaics at a London Underground (LU) station will be lost through redevelopment work, heritage campaigners have warned.