The opposition will seek the impeachment of Senate Speaker Nikom Wairatpanich for denying Democrat MPs the chance to debate during Wednesday's parliamentary session.
Mr Nikom abruptly closed the session after only seven of the 57 Democrat MPs listed to speak had debated Section 5 of the charter amendment bill. The section would remove the current ban on family members of MPs and holders of political positions from running for the Senate.
Opposition chief whip Jurin Laksanavisit said the impeachment move was agreed upon at a party meeting yesterday.
The opposition believed Mr Nikom's action might have violated Section 89 of the constitution dealing with the impartiality of a parliamentary meeting chairman. It also may have breached Section 122 concerning conflicts of interest, Mr Jurin said.
The opposition will petition the Senate seeking Mr Nikom's removal, he said. In a twist of fate, the petition will need to be submitted to Mr Nikom, who will have to decide whether it has grounds to proceed.
If the speaker approves the petition against himself, he would have to forward it to the National Anti-Corruption Commission (NACC) for investigation and a final ruling, Mr Jurin said.
He said the opposition whips will also submit a separate petition to the Constitution Court, asking it to rule on whether the section of the amendment bill dealing with Senate candidates violates Section 68 of the constitution.
Mr Nikom, meanwhile, said the opposition must state clearly what he had done wrong in its petition.
He insisted he had exercised his authority properly to end the parliamentary session as the opposition debaters were repeatedly making redundant remarks.
He said he would forward the petition to the NACC once it is presented to him.
Pheu Thai Party MP for Nonthaburi, Udomdet Rattanasathien, who is also an adviser to the government whips, said Mr Nikom had followed parliamentary regulations after another Pheu Thai MP, Payap Panket, proposed a vote to end the debate. He maintained that not every MP who registers to debate the charter amendment will be given the opportunity to voice concerns.
Also yesterday, 114 Democrat Party MPs and senators asked the Constitution Court to rule on whether the 2014 Budget Bill violates the charter.
The lawmakers, led by Senator Paiboon Nititawan and Wirat Kallayasiri, submitted a petition to Parliament President Somsak Kiatsuranont through Charoen Chankomol, asking him to seek the court's ruling.
The petition argues Section 27 of the Budget Bill, concerning budget allocations for the Office of the Judiciary (OJ) and Office of the Administrative Courts (OAC), and Section 28 relating to allocations for independent agencies including the NACC, might violate paragraphs 8 and 9 of Section 168 of the constitution. The two paragraphs say the state must provide an adequate budget to the National Assembly, the Constitution Court, the OJ, the OAC and constitutional organs including the NACC.