Sixteen green groups have demanded that Robin's Nest be made a country park as soon as possible and that its size be more than double the government's proposal.
The hill, located to the south of the border, is home to 70 percent of the butterflies found in Hong Kong, as 174 species of them have been recorded in the area.
The groups also said Robin's Nest is recognized as "the only obvious terrestrial ecological corridor between Hong Kong and mainland China."
It is also home to one of the most important bat colonies in Hong Kong, while a number of other rare animal species can be found there, including the Graminicola striatus and the Chinese rasbora, a rare freshwater fish.
In the 2017 policy address, the government announced a plan to make Robin's Nest, which spans about 500 hectares, into the city's 25th country park.
In December, environment chief Wong Kam-sing said it takes about two years for the statutory procedures to be completed.
But yesterday 16 groups, including the Conservancy Association, Designing Hong Kong, Green Power and Greenpeace, said the park should cover 1,120 hectares, with over 95 percent being government land. They said Robin's Nest has become a hot spot for hiking.