"Slavery practices" at palm oil plantations in Sabah, Malaysia, have affected thousands of Indonesian migrant workers and their children, the National Commission for Child Protection has announced.

Commission secretary general Arist Merdeka Sirait said Tuesday a fact-finding team sent to plantations in Sabah discovered tens of thousands of Indonesian migrant workers and their children had been "systematically enslaved".

"They are placed in isolated barracks with no access to transportation, making it impossible for them to leave the plantations. Nor do they have access to clean water, lighting and other facilities," Arist, a team member, told The Jakarta Post on Tuesday.