The non-government group, Gabriela, the National Alliance of Women in the Philippines, said prostitution is the worst "exploitation that can be done to women."
The U.N. report published Thursday said making prostitution legal would allow HIV prevention and treatment programs to be more accessible to sex workers and their clients, Xinhua reported.
"There is no evidence from countries of Asia and the Pacific that criminalization of sex work has prevented HIV epidemics among sex workers and their clients," the report said.
Gabriela Deputy Secretary General Gert Ranjo-Libang said prostitution violates women's rights.
"This U.N. report is widening the door for women's rights violation," she said.
"Even factory workers in the Philippines are deprived of their rights under the Labor code. They remain underpaid, working in very bad conditions, without access to health care, and prevented in forming unions."