Thousands of Catholics were led by Philippine nuns and priests in a protest in Manila against a proposed law that would provide free contraceptives in a bid to curb population growth.
The protesters, mainly dressed in red, gathered at a Catholic shrine to voice opposition to the planned legislation, which would also encourage families to have only two children in an effort to reduce poverty.
The proposal, which is expected to face a tough time getting through parliament, has angered the influential Roman Catholic Church in the Philippines which has led opposition and called Saturday's protest.
Dolly Cruz, a 61-year-old pensioner, attacked the proposal as "contrary to the laws of God".
"God gave humans the power of reason to decide what is right and what is wrong for themselves," she said. Police estimated the crowd at about 7,000.
President Benigno Aquino has strongly backed the law, saying in a statement before the rally that in a situation where couples "are in no position to make an informed judgement, the state has the responsibility to so provide".
The Philippines annual birth rate has been steadily declining, but the government points out that some of the poorest regions have the highest rates.
The law would use a government health insurance fund to provide birth control pills, condoms and other contraceptives for free.
It would give the poor preferential access to family planning services in state hospitals, while lessons on family planning and sex education would become compulsory in schools and for couples applying for a marriage licence.
The House of Representatives, dominated by Aquino supporters, is expected to pass the bill on Tuesday after failing to do so last year.
But the Senate, parliament's upper house, must also pass the law and has come out strongly against it.
Both abortion and divorce remain illegal in the predominantly Catholic Philippines.