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MANILA—The Philippines would waive its rights over the West Philippine Sea should it agree to a joint oil and gas exploration with China, former solicitor general Florin Hilbay said Saturday.

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"That's rather blatantly unconstitutional. It's against the decision in the Philippines vs. China, which declares that we don't have any overlapping entitlements with China over the West Philippine Sea. Which means that the potential oil and gas, such as Reed Bank, is entirely and exclusively ours," Hilbay told ANC.

"The moment you enter into some kind of an agreement such as co-ownership, you are recognizing the right of the co-owner, which will result in the waiver of the decision in Philippines vs China."

Included in a 2016 ruling by the Permanent Court of Arbitration in The Hague was a clarification of Manila's sovereign right to access offshore oil and gas fields, including the Reed Bank, within its 200 mile Exclusive Economic Zone.

Hilbay said the least that government could do is to file a diplomatic protest against China.

"I think at the minimum, we should've filed multiple formal protests already and yet up to this day we have not seen any move on the part of the administration to file even just a formal protest, which is a minimum requirement for these types of problems," he said.

The former solicitor general said the Philippines should team up with other claimants in the South China Sea to protest against Beijing.

"It doesn't have to be just us. Again, the minimum is to file protest because your rights are being trampled upon. Finding other countries for the same interest, who can be allies, and putting enough pressure on China," he said.

"There are many other countries in the area that have converging, overlapping coincidental interests with the Philippines. The size of these countries banding together would be a sufficient force against China, not in terms of fighting a war merely but in terms of putting enough diplomatic pressure to stop China from doing what it's doing now."

He added that fighting China does not necessarily mean going to war.

"In relation to China, all of those other countries that are asserting their rights are small as well, but they're able to do something. We shouldn't dichotomize this problem into submitting rather embarrassingly and giving everything away to China and just fighting a war with China. There's a large universe of options available for small countries such as ours," he said.

President Rodrigo Duterte earlier said that antagonizing China would not do the Philippines any good, as it cannot match the Asian nation’s military power.

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“You want us to wage war? Because I can. I can declare war against China tonight. But who will come? My soldiers and cops? They will just die,” Duterte said.

Since assuming the presidency, Duterte has chosen to downplay Manila’s sea dispute with Beijing, and instead sought to improve economic ties.