Opposition coalition 1Sambayan also joined the call to condemn Russia's recent military invasion of Ukraine and demanded to immediately withdraw its armed forces from the former Soviet republic.
In a statement, 1Sambayan said that the Philippine government must also oppose Russia's invasion to prevent such unlawful act from being legitimized by state practice.
"A successful Russian invasion of Ukraine will further embolden China to likewise use armed force to seize the West Philippine Sea from the Philippines," 1Sambayan explained.
The coalition's statement came after the United Nations General Assembly overwhelmingly voted to condemn the invasion of Ukraine which rings a global denunciation against Russia.
1Sambayan said the bedrock principle upon which the United Nations was founded is under Article 2, paragraphs 3 and 4 of the 1945 UN Charter which states that "all members shall settle their international disputes by peaceful means in such a manner that international peace and security, and justice, are not endangered."
"All Members shall refrain in their international relations from the threat or use of force against the territorial integrity or political independence of any state, or in any other manner inconsistent with the Purposes of the United Nations," it adds.
According to the coalition, this fundamental principle has prevented world wars since 1945 and has restrained powerful states from trampling upon weaker states.
"It has outlawed the old barbaric practice that war is a legitimate means of acquiring or annexing territory. It has changed the old principle that might is right into right is might," 1Sambayan said.
Russia’s recent invasion of Ukraine, 1Sambayan noted, is a blatant violation of Article 2 of the UN Charter, and President Putin's justification that Ukraine, a nation of 44 million people, is not a sovereign state and has no right to exist as a sovereign state is a "bare-faced lie."
Russia signed the 1994 Budapest Memorandum, along with the United Kingdom and the United States, expressly guaranteeing the sovereignty and territorial integrity of Ukraine in exchange for Ukraine giving up the huge stockpile of nuclear weapons that it inherited upon the dissolution of the Union of Soviet Socialist Republics.
"Ukraine, now a non-nuclear armed state, is a member of the United Nations and is recognized as a sovereign state by all the other members of the United Nations," it said.
Meanwhile, the Manila Declaration, which was unanimously approved in 1982 by the UN General Assembly, affirms the bedrock principle outlawing the use of force or threat of force to settle disputes between or among states.
"Such disputes should only be settled by negotiation, mediation or arbitration. The Philippines correctly invoked before the UN General Assembly the Manila Declaration in condemning the Russian invasion of Ukraine," the coalition said.
1Sambayan emphasized that the Philippines, being a founding member of the UN and a proponent of the Manila Declaration, has a "moral, historical and legal duty to uphold the fundamental principle of peaceful settlement of disputes between and among states."
"The world cannot allow Russia to resurrect and solidify by state practice what the UN Charter and the world have expressly rejected–that war is a legitimate means of acquiring or annexing territory," it said.
"The Philippines and all the states and peoples of the world, have a vital interest in invoking and preserving Article 2 of the UN Charter–that it is unlawful to use force or the threat of force to settle territorial or any kind of dispute between or among states," the coalition added.