The UN Committee on Enforced Disappearances asked Mexico for such figures after concluding a probe into the thousands of people it suspects have disappeared, including 43 students who went missing in southern Mexico in September.
"The committee noted with concern the lack of precise statistical information on the number of persons subjected to enforced disappearances," it said in its conclusions.
The committee's Luciano Herzon told reporters it was essential to provide such figures in order to devise policies to stop the problem.
Herzon said the government has given a "huge variety of numbers in different years," even as AFP has quoted officials in Mexico as saying more than 22,000 people have disappeared since 2006, when the government launched the war against drug cartels.
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The committee's Rainer Huhle said out of the thousands of enforced disappearances only "six persons (had been) put to trial and sentenced for this crime," suggesting criminals were acting with impunity.
"There is an apparent obvious discrepancy between the obligation of the state to punish and prevent this crime and its ubiquity in many parts of the country," Huhle said.
Human rights groups criticised Mexico's government saying the declaration that they had died was premature because unanswered questions remained in the case, especially since DNA tests had only confirmed the death of one student.
The relatives believe that the remaining students are still alive and suspect the prosecutor is just keen to close the case.
The committee made a special appeal on missing migrants, saying Mexico should "redouble its efforts" to find them through cooperation with their countries of origin, the victims' families and civil society.
The committee also called for the establishing of a system for quickly searching for missing people and, in cases of people who have died, returning their remains to their families.