The Philippines has flatly rejected a letter supposedly from a Filipino diplomat that's being cited by the Chinese embassy in Manila and being posted on its social media accounts to assert its illegal claim over Bajo de Masinloc.

Department of Foreign Affairs (DFA) Maritime Affairs spokesman Rogelio Villanueva, on Monday, March 16, issued a scathing statement rejecting and questioning a supposed letter issued by a Philippine ambassador in Germany to a radio operator in 1990.

There is "no merit" debating over the supposed document, considering that it is produced by third parties and presented as posts on social media.

It is even questionable, "especially if these third parties have vested interests and willfully misconstrue and misrepresent established facts," Villanueva asserted.

"As regards the recent letter posted by the Chinese Embassy in Manila, the DFA will not engage in conjecture or speculation over a document of uncertain origin and authenticity, and certainly without value," he said in a press briefing.

"China must be reminded that maritime and territorial claims are subject to established international legal procedures and dispute settlement mechanisms — not to unilateral proclamations or social media posts," he added.

If China really wants to argue with the Philippines' position on Bajo de Masinloc (or Scarborough Shoal) by citing such a document, it must do so in international venues.

"The proper venue for presenting these documents... we have international legal mechanisms and venues for presenting these documents for international legal scrutiny," he said.

Rogelio said China's persistent evasion of proper international legal scrutiny only speaks volumes.

"It betrays the utter baselessness of its positions," he said.

"A state confident in the legality of its claims does not shy away from international adjudication. China's conduct is a tacit admission that its claims cannot withstand legal scrutiny," he added.

The DFA maintained the Philippines' indivisible, incontrovertible, and longstanding sovereignty over Bajo de Masinloc and the Kalayaan Island Group.

Villanueva said the country has already duly proved and established its maritime claims through the 2016 Arbitral Award that has become an integral part of international law.

"The Philippines likewise consistently exercised and upheld sovereignty, sovereign rights and jurisdiction over its archipelago and other territories, including Bajo de Masinloc and the high-tide features of the Kalayaan Island Group (KIG), which is incontrovertible and firmly founded on international law and effective administration," he said.

While the Philippines welcomes continued dialogue with China, Villanueva said, Manila's pursuit of dialogue only reflects a calibrated and principled commitment to peaceful dispute settlement.

But it does not, in any manner, dilute or qualify the Philippines' firm, unequivocal positions in the West Philippine Sea, he said.

"Our sovereignty is non-negotiable. Our resolve is absolute," he added.