Distinguished researcher Kittikhun Peerasak Chanprateep, representing the group, said in the letter sent to the media that the caretaker prime minister had destroyed the political party system and in turn the parliamentary system.

A party leader was intended to represent members and deliver the party's policies to the people, but instead Thaksin had absolute control over the party, he said.

"We appeal to the Thai Rak Thai Party to consider an appropriate person to replace Thaksin because the party system and party policies are more important than one person. I don't want just one man to ruin the system," he said.

Kittikhun said in other countries if a party leader's legitimacy was called into question by even a little bit of doubt he would remove himself from important posts to avoid problems that might create divisions within his country.

"We urge the Thai Rak Thai to end Thaksin's regime before the party system is crippled," he said.