"From caring for children, to caring for elderly and persons with disabilities, to performing a wide range of household tasks, domestic workers are an indispensable part of the social fabric," Sandra Polaski, deputy director-general of the International Labour Organisation told reporters as she unveiled the agency's first report on the often invisible workforce.
Polaski said the majority of domestic workers, 83 percent of whom are women, are "often exploited beyond what would be tolerated for other workers."
They are forced to work longer hours and frequently are not allowed days off.
Their numbers surged from 33.2 million in 1995 to 52.6 million in 2010, according to the ILO report, which is based on official statistics from 117 countries.
That amounts to 3.6 percent of all wage earners globally, and 7.5 percent of all working women, the report showed, stressing that the percentages were far higher in some regions.
In the Middle East, for instance, a full third of all working women are domestic workers, while the number for Latin America and the Caribbean is one in four.
South and Central America are the regions that have seen the steepest hike in the number of domestic workers over the 15-year period, jumping from 10.4
million in 1995 to 19.6 million in 2010.
The report said the surge was in large part linked to the rising number of women entering the workforce in a region often lacking other options for child
and elderly care.
The UN agency stressed that its tally probably underestimated the real numbers, and pointed out that it did not include some 7.4 million child domestic workers under the age of 15.
It acknowledged that the real number of domestic workers in the world could be closer to 100 million, since such work often goes unreported.
"And the demand for domestic care workers will only grow in the future as societies age," Polaski said.
The report follows the adoption in June 2011 of a landmark domestic workers treaty aimed at ensuring decent working conditions and pay for such employees worldwide.
There is still a way to go, however, with domestic workers' rights especially lagging in the Middle East and Asia-Pacific regions.
Only 10 percent of all domestic workers are covered by general labour legislation to the same extent as other workers, the report showed.
At the same time, nearly 30 percent are completely excluded from such legal protections, as is the case for instance for basically all domestic workers in the Middle East.
In Asia-Pacific, where nearly half of the world's domestic workers live, 61 percent are excluded from national labour law protections.
More than half of domestic workers worldwide meanwhile live in countries that set no limitation for how many hours they can work each week, while 45 percent have no rights to weekly or annual paid rest periods.
Although they often work long hours with little or no holiday, domestic workers typically earn only 40 percent of national average salaries and only just over half are entitled to a minimum wage equivalent to that of other workers, the report showed.
"Combined with the lack of rights, the extreme dependency on an employer and the isolated and unprotected nature of domestic work can render them vulnerable to exploitation and abuse," Polaski pointed out.
And while women domestic workers often allow others to balance their work and family lives, they themselves often struggle to do the same: one in three have no right to maternity leave or benefits, according to the report.