Philippine president-elect Rodrigo Duterte says he will defy the Roman Catholic Church and seek to impose a three-child policy, putting him on a new collision course with bishops a day after he called them "sons of whores".

Key points: President-elect will push birth control law to boost economic growth

President-elect will push birth control law to boost economic growth Law was changed in 2012 allowing public health centres to hand out contraceptives

Law was changed in 2012 allowing public health centres to hand out contraceptives Church says it would continue to speak against government policies

The southern mayor has yet to be declared the May 9 poll winner, but an unofficial vote count by an election commission-accredited watchdog showed him ahead over his four rivals, three of whom conceded defeat.

Mr Duterte will assume office on June 30.

Mr Duterte's often outrageous comments have won him huge support and his tirades about killing criminals and a joke about a murdered rape victim do not appear to have dented his popularity in the largely Catholic country.

"I only want three children for every family," Mr Duterte said in Davao City.

"I'm a Christian, but I'm a realist so we have to do something with our overpopulation. I will defy the opinion or the belief of the Church."

About 80 per cent of the Philippines' 100 million population are Catholics, the largest concentration of any Asian country, who oppose abortion and contraception.

New economic advisor vows strong push for family planning

One of Mr Duterte's aides said the president-elect will aggressively implement the country's family planning law to push his economic growth agenda.

Sorry, this video has expired Dr Aries Arugay on Philippines Catholic Church relations under Rodrigo Duterte

Congress passed a law in December 2012, despite opposition from church leaders, allowing public health centres to hand out contraceptives such as condoms and pills and teach sex education in schools.

Mr Duterte is pushing for "rapid and sustained implementation" of the Responsible Parenthood and Reproductive Health Act, said Ernesto Pernia, an economic adviser to the tough-talking 71-year-old.

"If you enable families to limit and phase their children to what they can afford and what they can provide for, then that's going to have an effect on poverty and inequality," Mr Pernia said in an interview with ABS-CBN News Channel.

Church 'most hypocritical institution': Duterte

On Saturday, Mr Duterte criticised the Church as the "most hypocritical institution", meddling in government policies and said some bishops were enriching themselves at the expense of the poor.

"You sons of whores, aren't you ashamed? You ask so many favours, even from me," Mr Duterte said in an interview broadcast by TV station GMA.

Monsignor Oliver Mendoza, spokesman for the Archdiocese of Lingayen, whose head is the president of the Catholic Bishops Conference of the Philippines, said the Church respected Mr Duterte's opinion but that it would continue to speak against government policies that are contrary to Church teaching.

"Because if we fail to do that, if we close our eyes, if we close our lips, we close our ears, what will be the role of the Church?" he said.

Reuters