Prime Minister Hun Sen has knocked back a request by the opposition party to file a complaint to the International Court of Justice (ICJ) against alleged territorial encroachments by Vietnam.

Responding to the joint letter sent by 12 Cambodia National Rescue Party lawmakers on June 30, which demanded he take action through the ICJ against the Kingdom’s eastern neighbour, the prime minister reproached the opposition for ignoring the government’s efforts to resolve the border issue.

Without mentioning the ICJ by name, Hun Sen, in a letter sent on July 24, said the government considered defending the Kingdom’s sovereignty its most “important obligation”.

“[Our efforts] were not seen or pretended not to be seen by some circles,” Hun Sen wrote.

“This border problem has been taken [advantage of] in order to make political gains for [the opposition].”

The CNRP has of late stoked tensions by publicising alleged Vietnamese-built encroachments in border provinces including irrigation ponds in Ratankkiri, a road in Svay Rieng and military post in Kandal.

Among the government’s responses, Hun Sen cited diplomatic protests to Hanoi over the encroachments and his request for the constitutionally mandated original map from the UN to verify the border.

Opposition lawmaker Um Sam An contrasted the “weak” response with the government’s ICJ action against Thailand’s occupation of disputed territory in Preah Vihear province.