Ould Salek, the movement's foreign relations chief, urgently appealed to the UN Security Council on Tuesday to hold the referendum on the future of Western Sahara promised in a 1991 ceasefire agreement with Morocco.
He said "the situation remains very tense, very dangerous" in a buffer strip in southwestern Western Sahara where Moroccan security forces are facing Polisario Front fighters.
"Anything can start the confrontation," Salek warned.
A confidential UN document said Morocco violated the 1991 cease-fire agreement by sending armed personnel into the area without prior notice to UN peacekeepers.
It said the Polisario Front also violated the ceasefire when it responded by deploying its fighters.
In late August, UN chief Ban Ki-Moon expressed concern that the 16-year truce between Morocco and Western Sahara seperatists is about to fall apart.
"[I'm] deeply concerned over the tense situation that has developed in the narrow buffer strip in southwestern Western Sahara," he said.
This comment followed an incident in which Moroccan troops and separatists were "in close proximity to each other" in the buffer zone, a UN statement said at the time.
A 1991 ceasefire ended 16 years of fighting between Rabat and the Polisario Front.
It left the Morocco controlling of all of the territory's main towns and the Polisario confined to a narrow strip of the desert interior.
The far south was left as territory neither side could have a permanent military presence.
According to the truce arrangements no troops should enter the buffer strip.