Diane Abbott said the number of people killed in the Grenfell Tower fire to be "hundreds".
The shadow home secretary said she expects the death toll to be well above the 79 so far confirmed by the authorities.
The Labour MP for Hackney North and Stoke Newington blamed the disaster on Conservative attitudes to social housing.
"Grenfell House (sic) is not just an accident; Grenfell House is not just an unfortunate incident. Those hundreds of people that died is a direct consequence of Tory attitudes in social housing," she told a conference of the Labour Progress group.
Ms Abbott said the Tories see residents in social housing as "second-class citizens".