Australia pressured by human rights advocates over Cambodia

A leading human rights group has urged the Morrison government to threaten Cambodia's Prime Minister Hun Sen with trade barriers over its human rights record and a crackdown on the opposition.

The call by Human Rights Watch comes as concern remains about witnesses and journalists not being granted access to the trial of Cambodian opposition leader Kem Sokha.

Cambodian opposition leader Kem Sokha is on trial for treason charges.Credit: AP

Mr Sokha has been charged with treason over a speech he gave in Melbourne in 2013, in which he told supporters he had received advice from advisers from the US about changing the government.

Phil Robertson, deputy director of Human Rights Watch's Asia division, said Australia should join with the European Union, which has threatened to end preferential trade access unless Cambodia improves its human rights record.

The EU has set a February 12 deadline for a final decision on whether to withdraw Cambodia's duty-free market access to its trading market under its Everything But Arms scheme.

Australia has a smaller trading relationship with Cambodia but has granted the country’s products tariff-free access as a "least developed country".

"Given that Kem Sokha is on trial primarily for a speech on democracy he gave in Australia, the government should call into question the very basis of the proceedings against him,” Mr Robertson told The Sydney Morning Herald and The Age.

"Australia should work closely with the EU, the US and others to use trade relations to pressure Cambodia to improve its extremely poor record on human rights and labour rights.

"Politicians in Canberra should reflect on the fact that Australian consumers don't want goods produced by highly oppressed workers whose can't refuse overtime, don't earn decent wages, and face abuses and firings when they organise to protect their rights."

Labor MP Julian Hill said the Australian government had been "shamefully weak in speaking up for human rights and democracy" in Cambodia.

Hun Sen is facing a February 12 decision by the EU on whether to remove trade concessions over his government's human rights record.Credit: Reuters

If found guilty, Mr Sokha could face 15 to 30 years' jail.

One of his lawyers, Sopheary Meng, told The Sydney Morning Herald and The Age she was unsure if the trial would last the full three months. She said it was taking place in a small room, despite complaints this had limited the number of witnesses - including diplomats and journalists - from attending.

"I do not think any of his supporters are allowed to go inside the court room. Someone must ask permission first before entering the courtroom, even journalists," Ms Sopheary said.

The Department of Foreign Affairs and Trade said Australian embassy officials had attended all sessions of the trial and would continue to do so.

"In engagements with Cambodian authorities, Australia has expressed the importance of ensuring that Cambodia's judicial processes - including the trial of Kem Sokha - are conducted according to principles of due process, procedural fairness and judicial independence," DFAT said in a statement.

"The Australian government has raised, and continues to, our concerns with restrictions on free speech, association and political expression in Cambodia."