Opposition Democrat Party leader Abhisit Vejjajiva yesterday insisted his party is determined to overthrow the "Thaksin regime", saying the government had lost legitimacy.
He said the Democrats are ready to support popular movements conducted within constitutional limits.
Abhisit did not rule out the possibility of party MPs quitting in order to conduct the campaign.
"If it leads us to win the battle, we won't hesitate [to do it] with unity," he said.
"The Democrat Party is inviting everyone to join us in reforming the party in order to reform Thailand. Our aim is to uproot the Thaksin regime. If we succeed, we in the Democrat Party will not accept any post arising through unconstitutional means," he said.
Abhisit was speaking after chairing an urgent meeting with the party's executive committee and MPs to discuss what role the party should play in the protests.
Some MPs joining in
A Democrat MP, who asked not to be named, said some MPs had decided to join the "anti-Thaksin regime" protests, which are being led by former Democrat MP Suthep Thaugsuban.
"We appreciate the campaign and wish to become Suthep's main supporters when this parliamentary session ends," the MP said.
Even though the government insists it won the last election by an overwhelming majority, this is a "dictatorship of the majority", the source said.
He added that at the meeting, MP Pirapan Salirathavibhaga had called on those fighting against the so-called Thaksin regime to be brave enough to break the rules too.
However, he said, several other members of the party disagreed with these ideas, especially when it comes to MPs resigning.
He warned that the government would continue pushing through several bills even if the opposition MPs left the House, citing a similar case in 2000, when opposition MPs - led by the New Aspiration Party - began quitting to pressure then-PM Chuan Leekpai to dissolve the House.
He said Chuan ignored the call and continued working till the end of his term.
"Similarly in 2010, when red-shirt leaders called on Pheu Thai MPs to leave the House in order to pressure then-PM Abhisit Vejjajiva to dissolve the House, Thaksin posted a message on Facebook advising his party not to do such a thing," he said.