‘Signor 1857′, an album containing 35 works by various photographers, is at risk of leaving Britain if £121,250 cannot be found.
Earlier this year, the UK Government said the original 8 July deadline would be extended if a ‘serious intention’ to purchase the album was declared.
The news comes as an exhibition of Cameron’s work opens at the Metropolitan Museum of Modern Art in New York.
The New York show is billed as the first exhibition of her work in the city in nearly a generation.