Australian parliamentarian Mark Butler has sent a letter to Australian Minister for Foreign Affairs Julie Bishop asking what concrete action is planned in response to the dissolution of Cambodia’s main opposition party and the arrest of its leader.

“These actions destroy any chance of national elections due in 2018 being remotely free or fair,” reads the letter, which was signed Tuesday and posted late yesterday to the Facebook page of former opposition leader Sam Rainsy.

Cambodia National Rescue Party President Kem Sokha was arrested in September on widely decried charges of “treason”, and the party - the only legitimate competitor to the long-ruling Cambodian People's Party - was then dissolved on November 16 for allegedly fomenting a foreign-backed “revolution”.

“Are you able to advise me what concrete action, if any, the Australian government is considering to pressure the Cambodian Government to fulfil the promise of the 1991 Peace Accords and give the Cambodian people a free and fair election?,” Butler asked.

In September, after the arrest of Sokha, self-exiled former CNRP President Sam Rainsy met with both Butler and fellow MP Anthony Byrne. Rainsy claimed at the time that both representatives would petition the government to take action.

Neither Byrne nor Butler have responded to requests for comment, but last week the Australian Embassy in Phnom Penh told the Post that the government is “considering options”, though not sanctions.

That, Rainsy insisted, doesn't rule out all measures.

“It’s a matter of wording,” he wrote via email yesterday. At their September meeting, Rainsy proposed visa bans as a potential reaction by the Australian government.

“The fact is that pressure is building up - from more and more countries - on the Hun Sen government to reverse its totalitarian drift,” Rainsy added.

Since the dissolution, only the United States has taken a tangible step in response to the dissolution by pulling funding for the National Election Committee.