He said although 1997 Constitution include a provision that bans such politicians, the Constitution Court distorted the clause. The new constitution should clearly stipulate the ban this time.

Newin Chidchob, a deputy agriculture minister in the Chuan government who was given a suspended jail sentence in a libel case chose to stay on in his post.

Charan said the new constitution should make it easier to censure the prime minister by reducing the number of MP signatures required from two-fifths of the House to one fourth.

The Thai Rak Thai Party yesterday called on constitution drafters to model the new charter on the 1997 People's Constitution and ensure prime ministers are elected.

Acting deputy leader Pongthep Thepkanchana said the 1997 charter - abolished after the September coup - was considered the country's best yet because it was written by representatives of the people.

"In addition, my party would like to call on those tasked with drafting the constitution to speed up their work so the mandate is returned to the people as soon as possible," Pongthep said.

He said drafters should have little trouble improving weaknesses exposed in the 1997 document in nine years.

Coup leaders and anti-Thaksin Shinawatra groups believe the 1997 charter was riddled with loopholes the ousted leader's government abused to accrue overwhelming power.

Pongthep said future prime ministers must be elected members of Parliament.

If not, there could be a repeat of the bloody May 1992 protests that forced the resignation of appointed prime minister Suchinda Kraprayoon.

Another positive that should be retained is single-seat constituencies. Multiple-seat constituencies will disadvantage small parties, he said.

Party-list representatives elected by proportional representation should not be abolished, he said.

He said proportional representation was not like a "presidential system" where representatives "cannot censure a national leader".

Pongthep suggested proportional representation could be improved by lowering the threshold for election to 3 per cent of the total vote. It is currently 5 per cent.

And, a new charter should make it easier for members to hold censure debates against prime ministers and Cabinet members by requiring 101 votes to allow either.

It should include improved referendum mechanisms, allowing them to be used as "tools to end national crises".

Meanwhile, the Democrat Party proposed that the charter establish an election court to replace the Election Commission.

Spokesman Ong-art Klampaiboon said a court was better than a commission in deciding election-law violations.

Democrat Party leader Abhisit Vejjajiva proposed that aspiring MPs should still be required to be members of political parties and that the rule requiring them to be members of the party 90 days before candidacy registration should stay.

However, there should be exceptions to the 90-day rule for those who have never been MPs, MPs who have conflicts with their party, and MPs who been unfairly treated by their parties, he said.