The Constitutional Council dismissed an election complaint by the Sam Rainsy Party Friday, claiming it was not in its jurisdiction under election law.
The party had complained against the National Election Committee, for violation of people's rights by omitting names of eligible voters from last month's national election.
SRP lawmaker Yim Sovann said Monday the decision by the Constitutional Council was "not fair at all."
"We have enough evidence for them to decide on the complaint," he said. "This shows that the Constitutional Council has no independence, and there is nothing surprising about the letter, because Constitutional Council members are really CPP members."
The council had made a "political" decision, not a legal won, he added.
Hang Puthea, executive director of Nicfec, expressed regret at the council's decision.
"The Constiutional councils declared that its decision was fair, bu tin a democratic society, each fairness is supported by the other. But right now, this decision is not supported by the opposition party, so the fairness is in the mystery.
Constitutional Council spokesman Penn Thol declined further comment Monday.