Jailed opposition leader Kem Sokha was officially charged with treason yesterday, about 36 hours after he was arrested at his Phnom Penh residence and sent to a Tbong Khmum prison.

If Sokha is found guilty, his party could be dissolved based on new legislation that prevents party leaders from holding a criminal conviction.

Phnom Penh Municipal Court spokesman Ly Sophanna said prosecutors had sufficient evidence to charge the opposition leader under Article 443 of the Criminal Code for “conspiring with [a] foreign power”. The charge carries a prison term of 15 to 30 years.

“Kem Sokha, head of Cambodia National Rescue Party, was arrested by police for committing [a] red-handed crime related to a secret plan and the activities of conspiracy between Kem Sokha and foreigners, which causes chaos and affects the Kingdom of Cambodia,” a court statement read.

The statement alleges that the “secret plan” has been carried out since 1993 until present, as purportedly revealed in a 2013 video.

Sokha was arrested midnight Sunday after the video – in which he claims to have received US assistance in planning his political career – resurfaced online. He was questioned for more than four hours on Monday at Tbong Khmum’s Correctional Centre 3 by a team of three Phnom Penh prosecutors.

Article 80 of the Cambodian Constitution grants immunity to lawmakers unless they are caught “red-handed”, which defence lawyer Pheng Heng said wasn’t the case in Sokha’s arrest, which was based on a four-year-old publicly available speech.

“At midnight the police cannot simply go inside the house, unless they hear a sound asking for help,” he said.

National Assembly spokesman Leng Peng Long said they would convene a meeting about Sokha’s immunity “as soon as possible”.

“But red-handed crimes don’t require us to strip off the immunity in advance,” he said.

Kem Monovithya, the deputy public affairs officer for the CNRP and Sokha’s daughter, reiterated the party’s decision not to replace Sokha as party head, regardless of the consequences.

“[T]here is no point for anyone to assume the leadership role when they know they will be placed in prison or forced to be a puppet just to have a meaningless opposition to legitimize the upcoming election,” she said via message.

Earlier this year, a new law was passed giving the Supreme Court the power to dissolve parties if their leaders have been convicted of a crime. The law was used to oust Sokha’s predecessor, Sam Rainsy, who was subject to numerous politically tinged convictions.

Yesterday, Interior Ministry spokesman Khieu Sopheak appeared to go a step further, saying the party faced dissolution if they even defended Sokha. This, he said, would apply at all political levels.

“The commune, district, provincial and municipal councils, and the senators will be gone as well,” he said. “If the party gets dissolved, nothing remains.”

CNRP Deputy President Mu Sochua, however, rejected the charges against Sokha outright.

“It’s a set-up, totally political scenario,” she said. “[Sokha] has always preached nonviolence, peace and democracy.”

She acknowledged that failing to appoint a new president could lead to the CNRP’s dissolution “any day”, which she said would be a blow to democracy, as they had been elected by their voters to represent them.

“I want to serve them with my full ability,” she said.

Fellow Deputy President Pol Ham said the party had no plans to protest to “defend” Sokha.

“It is good if they dissolve the party since I also want to retire . . . I want to go to the pagoda since I am old now,” he said.

Meanwhile, lawyer Heng said all defence lawyers were denied access to Sokha yesterday, but would request his transfer to Phnom Penh.

“The guards said they cannot allow the lawyers to meet him unless the prosecution orders the chairman of the prison [to allow it],” he said.

Lawyers have not been informed whether Sokha was questioned by the investigating judge.

While Sokha’s wife, Te Chanmono, was allowed to meet him, she was not permitted to bring him medication, Heng said.

According to Sochua, Sokha suffers diabetes and requires daily medicine.

Kingsley Abbott, of the International Commission of Jurists, said in an email that the “allegations against Kem Sokha have all the hallmarks of being politically motivated”, which made a fair trial almost impossible. “The single largest challenge facing the Cambodian justice system is the lack of independent and impartial judges and prosecutors,” Abbott said, adding this arrest came during a period of “rapidly deteriorating” human rights.

“The Government appears to be systematically neutralizing dissenting voices ahead of the next election, including political opponents, human rights defenders, civil society and the free media.”