The poll backed by the International Labour Organization (ILO), conducted last year, found that some 5.5 million Filipino children, or about 18.93% of all those aged between 5 to 17 years, were child labourers.
A majority of the children (69%) were still in school as they worked, but were more likely to drop out than those who didn't work.
The survey also said the situation had worsened in the last 10 years, when an equivalent survey in 2001 found four million children, or 16 percent of the total, were working.
ILO country director Lawrence Johnson told a forum in Manila that unveiled the survey that "the root cause of child labour... is poverty. No parent wants to mortgage (his or her child's) future."
Officials warned that more than three million minors were engaged in hazardous labour such as work in mines, factories and on the streets, where
they were exposed to dangerous substances and unsafe conditions.
Labour Secretary Rosalinda Baldoz blamed the increase in child labourers on a rising population, but added detection rates had also increased.
But she conceded, "even with our economic growth, distribution of benefits is still a problem".
The survey found 42 percent of child labourers were helping their families in farms or on large plantations, she said.
"We should see to it that parents have enough income that they would not withdraw their children from school," Baldoz told reporters.