In a statement, Panelo defended President Rodrigo Duterte's crackdown on illegal drugs, which the UN says has led to over 27,000 deaths since the campaign began in June 2016.
"The 11 UN Special Rapporteurs' act of peddling a biased and absolutely false recital of facts, adulterated with malicious imputations against the constituted authorities, smacks of unpardonable intrusions on our sovereignty", Panelo was quoted as saying by Efe news.
"Let the enemies of the state and their supporters from foreign soil be forewarned that no amount of destructive narratives against this government will envelop it with the appearance of pretended truth to hoodwink the Filipino people in embracing it", the spokesperson added.
The group of 11 independent legal experts on Friday called on the UN to open an investigation into alleged human rights violations committed as part of the anti-drugs crackdown.
"We have recorded a staggering number of unlawful deaths and police killings in the context of the so-called war on drugs, as well as killings of human rights defenders", the experts said, adding that the law has been weaponized to "undermine press freedom and the independence of the judiciary".
The statement said the rapporteurs were also "extremely concerned over the high number of killings (...) being carried out in an apparent climate of official, institutional impunity".
Filipino police figures say 5,100 people have died during operations against drug dealers who resisted arrest.
Duterte's crackdown on illegal drugs was one of the cornerstones of his campaign.
Despite the violence, surveys show that he and his policies remain very popular and his political allies fared well at mid-term elections last month.
( With inputs from IANS )