Foreign Minister Prak Sokhonn justified the widely condemned arrest of opposition leader Kem Sokha to foreign diplomats in a closed-door meeting on Sunday, telling them Sokha committed a “clear act of treason”, and warning the international community to not “interfere”, according to a statement released yesterday.

The Foreign Ministry statement says Sokhonn began the briefing by showing the gathered ambassadors, chargés d’affairs and military attachés a video clip of the Cambodia National Rescue Party president claiming he received US assistance in planning his political career.

The video – in which Sokha discusses strategies used to oppose autocrats in Eastern Europe – is being held up as key “evidence” of a US-backed conspiracy to foment regime change through Sokha, who was charged on Tuesday with treason and faces 15 to 30 years in prison. “The strategy to gain power is common to every political party and doesn’t constitute an offence but it is how this strategy is built and who is behind it that constitute [sic] an offence,” Sokhonn is quoted as telling diplomats.

“The competent authorities – the judiciary police along with the prosecutor – taking into account . . . the continued broadcasting of the clip [it is still circulated now] and the content of that video clip, came to the conclusion that this constitutes an offence of flagrante delicto.”

The clause, traditionally reserved for stopping a crime in action, allows authorities to detain parliamentarians despite their legal immunity and has been used by officials to justify the arrest of opposition lawmakers in several cases widely considered politically motivated.

The footage, however, has been publicly available since being shot in late 2013 by the Cambodia Broadcasting Network in Australia.

An edited, condensed version of the clip was published by Fresh News about three hours before the arrest, after it emerged on a now-deactivated Facebook account that has released several posts detailing the purported conspiracy. Sokhonn acknowledged this, saying: “What you have seen is the short version. There is a longer version that reveals more and would surely constitute more weight on Kem Sokha’s guilt.”

He claimed the clip showed Sokha “confessed clearly” that the US had “told him what to do”, and suggested the conspiracy explained the strikes and demonstrations following the disputed 2013 national election. “For us, for me this is a clear act of treason. But let the court decide.”

Reached yesterday, Sokha’s lawyer Pheng Heng condemned the continued assertions of Sokha’s guilt by officials.

“In Cambodia the presumption of innocence has never been used during my career as a lawyer,” Heng said.

A Cambodian legal expert, who requested anonymity because of the case’s sensitivity, said though Sokha had used provocative words in the speech, his words did not suggest treason. “Treason is if you use guns or weapons, but if you use [US advice] to get support from the people, it’s not treason,” they said.

During the meeting, Sokhonn warned the international community to “respect Cambodia’s sovereignty” and to “not interfere and respect our law”.

In a statement yesterday, Cambodia’s permanent mission to the United Nations responded to criticism from the United Nations High Commissioner for Human Rights Zeid Ra’ad Al Hussein, who had said there appeared to be “no respect for due process” in Sokha’s arrest.

The Cambodian permanent mission claimed Cambodia’s government had been “unfairly impugned” as authorities had acted “in accordance with legal and judicial process”, citing the in flagrante delicto clause.

The provision requires judicial authorities to obtain a two-thirds majority vote from the National Assembly to proceed with a case against a lawmaker. Though the CPP does not hold a two-thirds majority, this has not stopped it from approving similar prosecutions against oppositon lawmakers in recent years.

The National Assembly’s permanent committee is set to meet this morning to discuss the case with a view to setting a date for a vote.