The Pheu Thai Party has threatened to boycott the controversial draft constitution in a letter to the National Reform Council (NRC).
Samart Kaewmeechai, former Pheu Thai MP for Chiang Rai, led Pheu Thai members to parliament Thursday to hand the note to NRC chairman Thienchay Kiranandana.
The letter demonstrated the party's opposition to the proposed charter, Mr Samart said, and they wanted NRC members to be aware of their objections before the council takes a vote on the draft on Sept 6.
Meanwhile, political analysts believe that if the proposed charter wins endorsement from the NRC and the public, politicians who have been condemning the draft as undemocratic will still have to run in elections under the new charter.
Mr Samart warned that a new government formed after the next general election would be weakened by the constitution and become a "lame duck".
Its administrative power would be overshadowed by the proposed National Strategic Reform and Reconciliation Committee, the so-called "crisis committee", he said.
The draft charter includes a clause establishing the crisis committee, which will be invested with special powers to intervene in a crisis by seizing powers from a government and parliament if such action is deemed necessary.
The panel would consist of the prime minister and the armed forces and police chiefs, among others.
Its special powers will last five years after the new charter is enacted.
Mr Samart said future political problems should be tackled through the democratic process by an elected government, rather than by the crisis panel.
"The party is ready to rally its supporters to boycott the draft if it is passed by the NRC and goes to a public referendum," he said.
He called for the National Council for Peace and Order (NCPO) to lift a ban on political gatherings and to allow all political parties to campaign and explain the draft charter to the public ahead of the referendum.
Pheu Thai's position follows the line expressed by former prime minister Thaksin Shinawatra, who called for his supporters and "democratic advocates'' to reject the draft charter, saying it would move the country backward.
He made the comments in Finland on Aug 14.
Political analyst Sukhum Nuansakul said the Pheu Thai and Democrat politicians only wanted to outwardly demonstrate anti-draft charter sentiments to show they were committed to democracy, and that they would run in elections anyway if the new charter passes the referendum.
Mr Sukhum said he believed that despite being undemocratic, the draft charter will win approval from the NRC and the public.
"Politicians' campaigns for a boycott of the draft will be futile and they will have to run in elections under the new charter anyway," he said. "Most politicians only want elections to take place. They have been frustrated with poll delays."
A Pheu Thai source from the Northeast admitted that the party had to mount a formal challenge to the draft charter because it wanted to maintain its image as a champion of democratic principles.
The source said this was despite many party members being well aware that they had no chance of defeating the draft charter at the referendum.
Yutthaporn Isarachai, vice-rector of the Sukhothai Thammathirat Open University, said it was not surprising that the draft charter has drawn criticism from politicians as it had been drawn up out of distrust for them.
He praised the draft charter for enabling people to participate more in decision-making and monitor politicians' actions through a citizens' assembly.
But he added that the proposed crisis panel would undermine an elected government and other political institutions.
Mr Yutthaporn also believed that despite their opposition to the draft charter, all political parties will eventually run in elections if it passes the referendum as otherwise they will lose their support base.
Justice Minister Paiboon Koomchaya, who is also a NCPO member, said Thurday that many politicians had spoken out strongly against the draft charter because they knew they would lose benefits when it is enacted.
Gen Paiboon said politicians should allow the public to decide the fate of the draft for themselves instead of trying to sway them.
Deputy Prime Minister Wissanu Krea-Ngam warned that those who tried to rally people to either boycott or support the proposed charter at the referendum could risk violating the NCPO ban on political gatherings.
If the NRC approves the draft charter, a referendum on it is expected to be held in January.
The Election Commission (EC) will be responsible for organising the referendum as well as educating voters about the draft charter ahead of the vote.
Mr Wissanu said the EC is expected to submit draft regulations on holding a referendum to the National Legislative Assembly for consideration next month.
Mr Wissanu also sought to allay concerns over the special powers that would be given to the crisis panel, saying that its primary duty would be to make recommendations on reforms to parliament.
Its special powers would be used only if the country faces a crisis and all other available measures fail to deal with the situation, Mr Wissanu said.