“True neutrality means knowing your own interests, taking positions based on your own interests and not allowing others to define your interests for you by default,” Bilahari said.

“[Cambodia and Laos] have some difficult choices to make. And if they should make wrong choices, they will confront Asean as a whole with difficult choices,” he said. “We may have to cut loose the two to save the eight.”

The remarks drew a rebuke on Tuesday from a group of Cambodian current and former diplomats writing on the pro-government website, Fresh News, who blasted Bilahari for “destroying Asean unity and centrality” and questioning whether he was acting as an “agent”.

As China calls, is writing on wall for US-Cambodia military ties?

“What we find repulsive is his arrogant and condescending tone, not just about our country, Cambodia, and Laos, but even towards our current Asean leaders, a behaviour unbecoming of a former diplomat,” they wrote. “He made a barrage of misleading and flawed claims that are intellectually deceitful and normatively detrimental to the region, especially Asean.”

They said Bilahari’s opposition to the two countries went back years, noting that he had expressed a “wish” on Facebook to expel Cambodia as far back as 2016.

They also questioned whether his advocacy for greater engagement in the Mekong to counterbalance China’s influence was an attempt to turn the area into a battleground of great power politics. Cambodia, they said, did not wish to take sides.

00:53

South China Sea: Don’t let China ‘walk over us’, says Pompeo during Asean meeting

South China Sea: Don’t let China ‘walk over us’, says Pompeo during Asean meeting

They suggested that Bilahari had forgotten the basic principles of Asean, such as non-interference in domestic affairs. “It is dangerous, irresponsible, even suicidal, to throw away those principles for the simple and obvious reason that Asean unity and centrality will be shaken to the core,” the Cambodian diplomats wrote.

Bilahari, however, remained unbowed and in comments to This Week in Asia mocked the suggestion he was an “agent”.

“Being, as the authors point out, senile and forgetful, I cannot remember whether I am an agent, and if I am indeed an agent, I cannot remember who I am an agent for, but even my fogged and addled brain dimly wonders: who would use someone senile and forgetful as an agent? I cannot take this sort of rubbish seriously.”

US-China rivalry will swing between cold war, cold peace: ex-Singapore minister

The term “wolf warrior” is more often used to describe a style of aggressive Chinese diplomacy that takes its name from an action film. Asked to respond, the institute’s deputy director Terence Chong stressed the centre’s independence and said its researchers and speakers were free to provide insights.

Cambodia and Laos are seen by many analysts as being more dependent than other Asean nations on China due to their relative economic weakness.

“Beijing has been ready to take up opportunities to work with Laos and Cambodia economically and support their states, regimes, and other domestic actors,” said political scientist Chong Ja Ian, an associate professor at the National University of Singapore.

Chong said neither individual Asean members nor the bloc as a whole had been as supportive of the two countries.

Chong said the spat between Bilahari and the Cambodian diplomats had revealed challenges facing Asean over its coordination, effectiveness and relevance.

The next US-China battleground: Chinese dams on the Mekong River?

“Such a situation suggests Asean is an organisation in need of reform,” he said.

Nanyang Technological University public policy and global affairs professor Dylan Loh said while expelling member states from Asean was possible, doing so would be a “grave” issue.