Prime Minister Tony Abbott is facing open revolt in Liberal Party branches in his own electorate over his support for a deal that will see a privately owned, for-profit aged care home built on public parklands overlooking Sydney Harbour at Middle Head.

Rank and file members of the Mosman and Balmoral branches will protest at the Liberal state conference on Saturday over what they see as a betrayal of long-term promises by Mr Abbott and other senior federal ministers to protect the heritage of the former Defence-owned site known as 10 Terminal.

"Largely at my instigation, the Howard government committed more than $115 million to the Sydney Harbour Federation Trust to preserve the natural and built heritage of places like North Head and Middle Head": Prime Minister Tony Abbott. Credit:Jessica Hromas

The naval heritage buildings of 10 Terminal will be extensively rebuilt to create an 89-bed retirement home known as The Cove.

High-end aged care facilities elsewhere on Sydney's lower north shore are charging upfront bonds of up to $2.6 million per unit to join.