The constitution draft in its current form refuses to accept the sovereignty of the people and tries to prolong coupmakers' powers, Pheu Thai party said in a statement on Saturday.
"Even after several revisions, the draft doesn't recognise the sovereignty of the people. It perpetuates the powers of the coupmakers and the institutions it set up," the statement said.
The charter will bring the country backward to the point economic problems cannot be solved and people's lives cannot improve.
"Importantly, it does not inspire reconciliation, a critical problem at present," it said.
The draft does not respect and have faith in the judgements of people, the owner of sovereignty, the statement continued. "It will bring about a weak coalition government and the prescribed mechanisms will lead to failures and more conflicts."
The party also cited damage to the economy as another reason.
"The government will lack credibility internationally. What it brings will be a major hurdle to foreign investments. No investor will risk putting its money in a country with such a weak government, with no policy cohesion."
As well, the new charter lacks a clear, comprehensive framework for reform that cover all institutions.
"It's a constitution that seeks to freeze democracy and doesn't want democracy to be the mechanism to solve the country's problems. People will end up being weak and be deprived of rights and opportunities. The country cannot move forward efficiently."
The party concluded by insisting the charter must not have elements to prolong the coupmaker's powers. It must accept people's voice and does not bar a group or party from taking part in democracy.
Key members of the party, however, on Friday, thanked the National Legislative Assembly, a body set up by coupmakers for not impeaching 248 MPs for trying to amend the 2007 constitution.
Several pro-democracy observers found the move humiliating since they view the NLA does not have the legitimacy to impeach anyone from the start.
Together with a number of senators, they tried in 2013 to amend the charter so all senators were to be elected. The National Anti-Corruption Commission, which also monitor cases of abuse of authority, found they had a conflict of interest because the same lawmakers who amended the charter could run in the next senators' polls.
