Anti-government protesters have refused to take part in the parliament's political reconciliation committee, rejecting it as a ploy to keep Prime Minister Prayut Chan-o-cha in power.
The People's Movement announced its decision in a statement issued at Sanam Luang on Wednesday.
"We declare that we will not accept and not join a committee to be formed by the government," the statement said.
The reconciliation panel was agreed on by the special joint parliamentary session last month as a means to solve political problems highlighted by continuing student-led protests against the government.
The statement renewed its call for the departure of the prime minister,.
Gen Prayut Chan-o-cha's remaining in power was a major obstacle to resolving the country's political, economic and social problems, the statement said.
It also reiterated other demands, including writing a new constitution and reform of the monarchy.
Former prime ministers Anand Panyarachun, Abhisit Vejjajiva and Chavalit Yongchaiyudh have hinted they may be willing to join the proposed reconciliation committee, Parliament President ChuanLeekpai said on Tuesday.
