Philippine President Rodrigo Duterte is helped by interpreters to attach an earphone as he attends a luncheon meeting with Japanese business leaders in Tokyo, Japan, October 26, 2016. REUTERS/Kim Kyung-Hoon

Philippine President Rodrigo Duterte has maintained a significant level of public support since taking office this summer, despite the bloodshed caused by his drug war and his often erratic behavior on the world stage.

But there is at least one high-profile Filipino who's exasperated by the brusque pronouncements of President DU30, as Duterte is known.

"In his consistently frequent insulting diatribes against the US, EU, and the UN, in which President Du30 also keeps complaining against the December, 2015, Paris Agreement on Climate Change (crafted by 195 nations, the Philippines included), he is unwittingly shooting himself in the mouth, and also all of us, 101.5 million Filipinos," Fidel Ramos, Philippine president from 1992 to 1998, wrote last week in the newspaper Manila Bulletin.

"He may claim that to be more 'insulting than friendly' to our long-established allies is part of his God-given 'destiny,'" Ramos continued. "But, this is obviously wrong, and full of S…. T !!!."

Ramos was inveighing against Duterte's attitude toward the international agreement to address climate change made in Paris late last year, which the current Philippine president has called "stupid" and "absurd."

Former Philippine President Fidel Ramos speaks to journalists during a trip to Hong Kong, China, after a Hague court's ruling over the maritime dispute in South China Sea, August 12, 2016. REUTERS/Tyrone Siu/File Photo

Duterte said his government would not honor the deal, as it would hinder the country's industrial growth, according to the Inquirer.

Ramos had served at Duterte's special envoy to China before stepping down this week in the wake of Duterte's trip to Beijing, which appears to have yielded some progress on Manila's access to Scarborough Shoal, a longstanding point of contention between the two countries.

Despite his role of envoy, Ramos has lashed out at Duterte before.

In early October, the former president wrote, "we find our team Philippines losing in the first 100 days of DU30's administration — and losing badly."

"This is a huge disappointment and let-down to many of us," Ramos went on.

Duterte, in Ramos' estimation, had failed to get results on issues like alleviating poverty, improving quality of life, and enhancing public security in his first 100 days in office — which he could've addressed "if he had hit the ground running instead of being stuck in unending controversies about extra-judicial killings of drug suspects and in his ability at using cuss-words and insults instead of civilized language."

Ramos, who also headed the Philippine armed forces, bashed Duterte for the latter's hostility toward US-Philippine military cooperation.

President Rodrigo Duterte, center, clenches a fist along with other Philippine Air Force (PAF) officials during the 250th Presidential Airlift Wing (PAW) anniversary at the Villamor air base in Pasay City, metro Manila, Philippines, September 13, 2016. REUTERS/Romeo Ranoco

"Are we throwing away decades of military partnership, tactical proficiency, compatible weaponry, predictable logistics, and soldier-to-soldier camaraderie just like that?? On P. Du30's say-so???" Ramos wrote in early October.

Other Philippine politicians, particularly those in the legislature, have criticized Duterte for his policies, especially his ongoing violent crackdown on drugs and drug use. But Ramos' stature may make his continued denunciations of the current president more salient — and more costly for Duterte.

"The primary risk is that Duterte will open up power struggles on too many fronts and find himself at odds with too many powerful enemies," regional-analysis firm Stratfor wrote in late August, roughly two months into Duterte's term.

A member of the Philippine National Police (PNP) stands guard while residents look on near the scene where two suspected drug pushers were killed during a police operation, in metro Manila. Thomson Reuters

This, Stratfor argued, could lead "to political instability such as that which plagued the Philippines from the late 1980s through the early 2000s."

A survey in September put Duterte at a +64 net approval rating, meaning he had widespread public support.

And, more recently, Duterte's apparently successful engagement with China over Scarborough Shoal seems to have won Philippine fishermen renewed access to the waters there.

But Scarborough may yet prove to be a lightening rod: Should the nascent Manila-Beijing detente in the South China Sea fall apart, and Manila's position on matter worsen, Duterte may find himself facing backlash from both Ramos and many of their countrymen.