Jakarta: Federal Labor MP Julian Hill has launched an extraordinary attack on Cambodia's Prime Minister Hun Sen, declaring the dictator has sold out his country to China and warning the rising superpower is using the same tactics it used to militarise the South China Sea.

Mr Hill, whose seat of Bruce is home to one of the largest Cambodian-Australian populations, said that on the eve of the 28th anniversary of the Paris Peace Accords that ended Cambodia's long and bloody civil war, democracy was dying.

The MP recently spent a week in Cambodia on a self-funded study tour where he met with civil rights groups, union activists and the remnants of the now-banned political opposition.

"Australia and the world made a promise to the Cambodian people, to stand up for human rights, peace and democracy. But 28 years on, the world has failed to keep its promise," he told Parliament.