Human Rights Watch on Monday urged the Security Council to task UN peacekeepers in Western Sahara with rights monitoring, accusing Morocco of suppressing dissent in the territory it controls.
The call, in a letter addressed to the Security Council, comes ahead of the annual vote next week on renewing the mandate of the peacekeeping mission, known as MINURSO.
It is a move fiercely opposed by Morocco, which annexed the former Spanish colony in the late 1970s in a move never recognised internationally.
On Saturday, King Mohamed VI warned Ban Ki-moon against "dangerous options" after the UN chief called for "sustained, independent and impartial" human rights monitoring in the disputed region and the refugee camps in western Algeria run by the pro-independence Polisario Front.
"Morocco has announced a series of human rights initiatives since 2011 that, while positive, have yet to change the basic human rights situation in Western Sahara," HRW said in its letter.
"That situation is characterised by Morocco's firm repression of all Sahrawis who express their opposition to Moroccan rule and who favour self-determination for the territory," said the rights watchdog.
It said its own monitoring of the human rights situation in Western Sahara, which included recent visits to the territory's two main cities and the Polisario-run camps, confirmed the need for sustained, independent and impartial monitoring as advocated by the UN chief.
Signup to our newsletter and follow us on Facebook and Twitter!
"Existing rights-monitoring mechanisms fail to meet these criteria," said the New York-based group.
"Impartial UN monitoring makes it more difficult for parties to distort claims of human rights violations to promote their political agendas. It deters abuses and promotes accountability -– all essential to promoting stability and political settlements," it added.
Unlike UN peacekeeping forces elsewhere, MINURSO, which has monitored a ceasefire between Morocco and the Algeria-backed Polisario Front since 1991, is not charged with reporting on human rights, something rights activists and the Polisario have advocated for years.
Washington sought last year to enlarge the peacekeeping force's mandate, an unexpected move strongly opposed by Morocco, which controls most of the territory and is highly sensitive to criticism of its policies there.
The proposal was finally dropped after Rabat launched a shrill lobbying campaign.
Morocco has proposed wide autonomy for Western Sahara under its sovereignty, as a solution to the decades-old conflict.
This is rejected by the Polisario, which has campaigned for independence since 1973, and insists on the right of the Sahrawi people to determine their own future in a UN-monitored referendum.