Residents are said to be shocked and worried
Tenants living on estates in inner London which are owned by the Crown, want the Queen to intervene to stop their homes being sold off.
Residents in homes owned by Crown Estates fear rents could go up and key workers be forced out if they are sold.
Protesters have marched to Buckingham Palace and delivered a petition.
Crown Estates, which has 1,300 homes in Victoria Park, Regent's Park, Millbank and Lee Green, said residents had been being consulted about the proposals.
Joannie Andrews, of the Victoria Park Crown Residents Association, said people living in the Crown Estate's homes in London had been shocked by the announcement.
Elderly and vulnerable
Ms Andrews said: "Since the 1960s a lot of the tenants here have been teachers, social workers and other key workers who made a huge contribution to the improvement of what was until fairly recently a predominantly working class area in Hackney and Bethnal Green.
"Some of these people - many of whom still live on the estate - are now quite elderly and vulnerable."
She said an eight-week consultation period had been given.
"People I've spoken to are really shocked and worried for their future," she said.
Paul Clark, of The Crown Estate, said: "It's important to remember that at the moment we only have a proposal, and yes the proposal does say we're considering a sale, but that's with a number of conditions.
"At the moment no decision has been made."