Former king Norodom Sihanouk launched a fresh reminder of the failures of the royal family in politics this week, writing in a communique that political involvement for royals had led to severe punishments and exile.

"The pain and humiliation of Khmer princes and princesses who get involved in politics is far reaching," Sihanouk wrote in French.

The participation of royal family members in politics remains a contentious issue in Cambodia. Critics say they should avoid politics altogether, even if there is no law to ban them.

Neither royalist party faired well in July's election.

The Norodom Ranariddh and Funcinpec parties each won two of 123 National Assembly seats.

The former monarch's communiqué was an apparent reference to his son, Prince Norodom Ranariddh, who is leading his self-named party from exile in Kuala Lumpur and faces a jail sentence and fine if he returns.

Prince Ranariddh was not available for comment.

Prince Sisowath Sereyroth, a member of Funcinpec, said this week that a ban on royal family members from politics would be unfair and would mark the abandonment of one group of Cambodians.

"I am Khmer," he said. "I want to help Khmers when I see the country going in an improper way".

In Thailand, another monarchy, princes are involved in politics, he said.

Prince Sereyroth noted that Sihanouk was known for his politics, bringing peace to the country that did not come under the Lon Nol, Khmer Rouge or State of Kampuchea regimes.

"It should not be forgotten that only the king can bring peace," he said. "And if we have peace, do not forget that."