About 20 sites within or close to two country parks in Sai Kung are vulnerable to the type of development that is blighting a pristine coastal spot at Sai Wan.
They are not covered by any statutory zoning plans and at least two are already damaged as a result of illegal construction work.
Environmentalists want the planning loophole plugged with urgent zoning of at-risk sites or the government stepping in to buy the land to save it from destruction.
But the government says rezoning would be of little help in the Sai Wan case, where vegetation has already been removed, and it refused to say what, if anything, was being done about the other sites, saying it was 'sensitive information'.
Last week, the South China Morning Post reported that businessman Simon Lo Lin-shing bought an abandoned village on the scenic Tai Long Wan coast at Sai Wan and was stripping bare a site for a private retreat.
Secretary for Development Carrie Lam Cheng Yuet-ngor rejected the buyout option, saying it was unaffordable and that there was no current policy under which it could be done.
She said zoning of the sites as a development permission area, with enforceable land-use zoning rules before a detailed zoning plan was drafted, would not make a big difference to the Sai Wan site.