Hun Sen made the comment at the annual ceremony to mark Jan. 7, 1979, when Vietnamese-backed forces ousted the Khmer Rouge from Phnom Penh.
Prime Minister Hun Sen will join other Asean leaders for a special meeting with US President Barack Obama in California next month.
Sam Rainsy is in exile abroad, facing a jail sentence if he returns to Cambodia, in a defamation case brought by the president of the ruling Cambodian People’s Party, Heng Samrin.
Hun Manet made the defense in a video clip posted on the prime minister’s official Facebook page Wednesday, amid heightened political tensions over the border.
Human rights groups and land activists have accused the parliament of only offering blessings to dignitaries, and ignoring the voters who elect its 123 members.
Hun Sen also announced that he would not offer his signature for an amnesty petition for Sam Rainsy and other Cambodia National Rescue Party leaders.
Sam Rainsy said that the use of insults in politics should be brought to an end in favor of peaceful negotiations to serve the nation’s interests.
At least 10 Rescue Party activists and supporters are currently in detention, on various charges, including Hong Sok Hour, an aging senator who has been jailed since August.
The boycott was a result of anti-opposition protests in November that led up to the severe beatings of two opposition lawmakers outside the Assembly.
Norodom Ranariddh said Friday he would be interested in a coalition, rather than being a party in the opposition role, if Funcipec regained voters.
Rights and development groups say a draft law on access to information will be more useful to the public if it has input from outside the government.
Thailand Saturday celebrated national day and the birthday of its king, Bhumipol Adulyadej, with tributes and ceremonies.