The Democrats have condemned the Pheu Thai Party for making what they call groundless accusations of conspiracy against the Constitutional Court.
The ruling party on Friday accused the court of being part of a plan to remove caretaker Prime Minister Yingluck Shinawatra because it will try her over the removal of Thawil Pliensri.
Pheu Thai said the case was part of an attempt to install a neutral, unelected prime minister in her place.
Democrat Party deputy leader Ong-art Klampaiboon said yesterday Pheu Thai MPs were pointing the finger at the wrong person, as it was Ms Yingluck who ordered the removal of Mr Thawil as National Security Council (NSC) secretary-general in 2011.
"I want the Pheu Thai Party and Ms Yingluck to read again the verdict of the Supreme Administrative Court," Mr Ong-art said.
The court ruled last month that the removal of Mr Thawil was unlawful. It explained that although the prime minister was authorised to transfer officials, the transfer must be free from bias and political preference.
The decision led to a group of senators to petition the charter court to consider the status of Ms Yingluck. The court's acceptance of the petition has riled the Pheu Thai Party.
Mr Ong-art said the accusations against the court by Pheu Thai MPs were an attempt to put pressure on the judges to "direct their ruling" in favour of Ms Yingluck.
He believed the court may rule after the Songkran holiday.
The Democrats also rejected Pheu Thai strategist Pokin Polakul's comparison of Ms Yingluck's case with that of Democrat leader Abhisit Vejjajiva. The Constitutional Court earlier decided not to consider whether to terminate Mr Abhisit's status as an MP after he was accused of avoiding the military draft, because the House was dissolved and he was no longer an MP.
Democrat spokesman Chavanond Intarakomalyasut said the cases were different as Ms Yingluck is still caretaker premier.