Gulf countries must end their sponsorship system for migrant workers that leaves labourers beholden to employers and exposed to potential abuse, the UN High Commissioner for Human Rights said on Monday.

"Reports concerning this region consistently cite ongoing practices of unlawful confiscation of passports, withholding of wages and exploitation by unscrupulous recruitment agencies and employers," Navanethem Pillay said in a speech at Saudi Arabia's first mixed-gender university in the port city of Jeddah.

"Some are held in prolonged detention after they escape abusive employers and may be unable to obtain access to judicial recourse and effective remedies for their plight."    

The world's largest oil exporting region has attracted tens of millions of mostly blue-collar migrants from Asian countries, many of whom work in construction or as domestic maids.

Many workers complain that agencies or employers confiscate their passports for the duration of their contracts, do not pay them regularly or deduct housing or health costs from their pay.

Some Gulf countries such as Bahrain are scrapping the sponsorship, or kafala, system, while others such as Kuwait are overhauling labour laws or introducing a minimum wage to improve the conditions for millions of foreign workers.

But Saudi Arabia, where expatriate workers comprise 7 million of the 25 million-strong population, has yet to make such reforms as diplomats say there is resistance among businesses who benefit from the system.

Pillay said she welcomed plans by some Gulf countries to reform the kafala system, but urged others to follow suit.

"I wholeheartedly support those efforts and call on other states to replace the kafala system with updated labour laws that can better balance rights and duties," Pillay said, according to a draft copy of her speech emailed to the media. - Reuters