House Speaker Wan Muhamad Noor Matha has asked the opposition to remove any mention of former premier Thaksin Shinawatra from the no-confidence motion against Prime Minister Paetongtarn Shinawatra.
The motion was submitted to Mr Wan, who, after reviewing it, informed opposition leader Natthaphong Ruengpanyawut that any reference to Thaksin must be removed.
Mr Wan argued that directly referencing Thaksin, an outsider in the debate, would violate parliamentary meeting regulation No 176.
The opposition, however, is unlikely to budge.
Parit Wacharasindhu, a list MP and spokesman for the opposition People's Party, objected to Thaksin's omission from the debate.
He insisted that neither the constitution nor parliamentary rules grant the House Speaker the authority to determine the content of a no-confidence motion.
Furthermore, he argued that regulation No 176 does not require amendments to a motion unless its filing process was flawed.
Mr Parit added the motion could no longer be amended since it was submitted more than seven days ago -- the maximum period allowed for revisions.
"The House Speaker lacks the authority to mandate a revision in this case," he said.
Mr Parit said parliamentary rules permit debaters to reference third parties if the mention is relevant to their involvement in national administration.
The censure motion, which targets Ms Paetongtarn exclusively, accuses Thaksin of exerting influence over his daughter's administration.
The no-confidence debate, which the government wants to limit to a single day -- contrary to the opposition's demand for a five-day discussion -- is set to take place at the end of the month.
Mr Parit said Thaksin himself has openly admitted to interfering in government affairs.
Earlier, Mr Wan warned that an unrevised motion could expose lawmakers to defamation lawsuits from the outsider in question.
He argued it would be unfair for someone who is not present in parliament to be unable to defend themselves.
Meanwhile, Prime Minister's Office Minister Chousak Sirinil expressed concern that, despite focusing on the premier, the debate could be diverted into attacks on cabinet ministers.
PP deputy leader Sirikanya Tansakul said Mr Natthaphong had responded to Mr Wan, asserting the opposition would stand firm and refuse to alter the motion, citing legal privileges.
She pointed out that regulation No 176 merely advises that debaters should avoid mentioning outsiders unnecessarily.
"But if an outsider has a role in national administration, they warrant a mention," Ms Sirikanya said, adding the opposition is fully aware of the legal risks associated with referencing a third party.
Ms Sirikanya urged the government not to overreact to the motion.