The International Labour Organisation on Thursday passed a landmark treaty giving protection to an estimated 52.6 million domestic workers across the world.

The new convention would ensure domestic workers enjoyed conditions "not less favourable" than other workers, requiring governments to ensure they understood their rights, preferably through written contracts.

The document also offers domestic workers a full rest day every week, and prevents them being required to remain with an employer's household during their annual leave or rest days.

The convention, which was adopted with 396 votes for, 16 against and 63 abstentions, will come into effect upon the ratification of two countries. The Philippines and Uruguay have already said they would ratify the accord.

"This is a historic moment at the 100th session of the International Labour Conference, and we are making an important turning point," said a United Arab Emirates envoy, speaking on behalf of Gulf states, all of which supported the treaty.

ILO data, which is a compilation of national statistics, indicate that there were at least 52.6 million domestic workers worldwide in 2010.

But there are reasons to believe that the true number, concealed by undercounting among some states, could lie close to 100 million, the agency added.

Despite the large numbers, domestic workers are still among the most exploited and abused.

Many are required to work irregular and long hours for low pay and are given insufficient rest. Live-in domestic workers in particular, can be on call at all times of the day.

They are also largely excluded from social protection such as maternity benefits and social security.

Nevertheless, joining the convention is only the first step. Countries would not have to implement the treaty until ratification, while others can also opt not to sign up, which could reduce its bite.

While it has secured the support of countries ranging from the United States, Indonesia, and Brazil, others, such as Britain, abstained.

Britain said it could not vote for the convention as it was "unable to ratify in the foreseeable future."

It noted for instance that it was not practical to apply the same health and safety standards, including inspections, to private households employing domestic workers.

It added that it would be "inappropriate to hold elderly individuals... to the same standards as large companies."

But supporters of the convention and activists believe that the strength of the treaty is that it sets a standard.

"There's an understanding that major sending countries... are in support. They will want the protection that will be provided when dealing with other countries," South Africa's chief negotiator Virgil Seafield told AFP ahead of the vote.