The opposition CNRP has said it is not responsible for the actions of people linking the party to convicted criminals.
The opposition is distancing itself from anyone using the voice, picture, or documents of convicted criminals following recent amendments to the Law on Political Parties.
The amendments are widely seen as being aimed at former CNRP leader Sam Rainsy who faces several jail terms if he returns from exile.
Party spokesman Yim Sovann said the CNRP issued a statement to prevent anyone with bad ideas from attacking his party by any means.
He declined to explain in more detail, saying the meaning is already set out in the letter.
CPP spokesman Suos Yara said the Law on Political Parties applied to big and small parties.
He said CPP lawmakers passed the law to strengthen the state and defend peace against populism and a colour revolution.
Political and social analyst Lao Mong Hay said it was right for the CNRP to put out the statement, but the party should do more.
“They should send a letter to the court to recognise this problem,” he said.
After the court recognised it, the party should ask that the statement be published in the royal gazette, which would make it recognised officially by the government, he added.