The Sam Rainsy and Human Rights parties on Monday filed complaints over July's election results with two representative countries of the 1991 Paris Peace Accords.
The ruling Cambodian People's Party and the National Election Committee had violated the Accords and denied Cambodians a democratic election, the parties said Monday in complaints to France and Indonesia.
Opposition leader Sam Rainsy said he wanted the countries to intervene, but he declined to say how. The Accords require democratic elections, and Sam Rainsy said July's election had not been democratic.
The CPP has warned that the parties must participate in a swearing-in ceremony of the new National Assembly, scheduled for Sept. 24, or risk having their seats reallocated among other parites.
Both parties reiterated their plan to boycott that meeting in protest of the election results Monday.
Human Rights Party President Kem Sokha said the 18 national signatories to the Accords had a responsibility to ensure free and fair democratic elections.
"They must not only sign, but they have to follow what happens in Cambodia," he said. "Cambodia is not alone."
Sam Rainsy said more than 20,000 people had thumb-printed a petition claiming they were denied their right to vote in the election.
As many as 800,000 administrative forms had been fraudulently issued during the election, allowing nearly 1 million people to vote who were not eligible under election law, he said.
NEC Secretary-General Tep Nitha said Monday the parties had a right to complain to the international community, but the election body had done what the election law required.
Hang Puthea, executive director of the Neutral and Impartial Committee for Free and Fair Elections in Cambodia, said countries that signed the Peace Accords should issue some kind of response to the complaint, in order to demonstrate their continued roles in free and fair elections in Cambodia.
This is the first time parties have complained using the Accords, he said.
The complaints could cause the National Election Committee to pay more attention to regulations for the next election, he said.