He dismissed the CDC's reasons that appointing senators would solve the problem of nepotism in both chambers of Parliament and the failure of the Senate to check on the Lower House because of that.

The Democrats had proposed that senators should represent constituencies larger than a province or citizens should be allowed to vote across provinces. Rules and criteria for Senate candidates should also be tightened, he said.

Thai Rak Thai caretaker leader Chaturon Chaisang said his party would not launch a public campaign to vote down the constitution even though the CDC had move to slash the number of constituency MPs - from 400 to 320.

Reducing the Lower House's membership would make MPs quarrel over responsibilities, because they will have to look after more constituents. The resulting conflicts among MPs would weaken the party system.

He expressed concern over the move to appoint senators, pointing to a potential conflict of interest if senators continue to appoint and remove members of independent organisations while members of independent agencies are included in the senator selection panel.

The party would decide whether to accept or reject the charter draft before the public referendum, he added.

Deputy Chat Thai leader Veerasak Kowsurat disapproved of the CDC's move to cut constituency MPs from 400 to 320, saying that would lead to fierce competition in elections and make vote-buying inevitable. It would also not let new parties and new candidates enter politics.

Former senator Wiboon Chaemchuen opposed the proposal to appoint senators, saying that if the duty of senators was to impeach politicians, they should be elected for such a critical job.