The UN statement came ahead of a key decision by the House of Representatives on Tuesday on whether to end debates and vote on the bill that has been pending for 11 years.
"Enacting a law that would address the reproductive health needs of the Filipino people would, over time, vastly improve health and quality of life and support development," it said.
The UN warned that if current population trends continue in the Philippines, the number of people living in poverty would increase despite strong economic growth.
The bill would require the government to make contraceptives available to the poor and to provide educational programmes on the full range of family planning options.
The law would also provide for some sex-education for pre-teens, a particularly contentious issue for the Catholic Church, but an initiative welcomed by development groups.
"Hopes of future prosperity could turn to dust if the country is not able to deal with the population growth by giving men and women access to the information and means to freely and responsibly exercise their human right to have just the number of children they want," the UN said.
The Philippines' population is projected to hit 97.6 million this year and to top 100 million in 2014, according to the Commission on Population.//DPA