The Democrat Party yesterday claimed that bogus witnesses were being called to falsely implicate party leader Abhisit Vejjajiva and MP Suthep Thaugsuban as they fight murder charges.
The two have been charged with ordering the killing of anti-government protesters during the 2010 unrest in Bangkok.
Democrat list-MP Ong-art Klampaibul said he had received information that fraudulent witnesses, both state officials and civilians, were being coached to fabricate accounts in the case. He provided no evidence to support his claims.
The witness accounts will be used to establish what roles Mr Abhisit and Mr Suthep played in instructing security forces to deal with the protesters, Mr Ong-art said.
Ninety-one people were killed in Bangkok and the provinces during the 2010 crackdown, including Phan Khamkong, a 44-year-old taxi driver.
The Criminal Court ruled on Sept 17 that the taxi driver, from Yasothon province, was killed by security forces near the Ratchaprarop Airport Link station on the night of May 14, 2010.
Citing the findings of a tripartite team of investigators from the Department of Special Investigation (DSI), police and prosecutors at a meeting on Thursday, the DSI charged Mr Abhisit and Mr Suthep Thaugsuban with murder for their alleged involvement in the killing.
The DSI's decision was based on the court's Sept 17 ruling, DSI chief Tarit Pengdith said on Thursday.
The decision marked the first charges brought against members of the Abhisit administration over deaths during the 2010 red-shirt rallies.
Mr Ong-art also accused the government of meddling in the DSI's investigation,saying that certain figures in the government had announced weeks ago that Mr Abhisit and Mr Suthep would face charges, before the DSI had actually pressed the charges against them.
He said that made him believe the charges had been ordered by the government.
The charges had been laid without any proof of who had killed the taxi driver, Mr Ong-art said, adding the DSI simply cited the court's ruling on Phan's death to justify the charges.
Meanwhile, Pheu Thai spokesman Prompong Nopparit denied the charges had been laid to pressure the opposition into bowing to the government's attempts to grant an amnesty to former premier Thaksin Shinawatra.
The two made the claim during speeches to a gathering of opposition supporters at Rangsit University on Saturday night.
Mr Prompong said the two murder suspects should stop making false claims, as they were distorting the facts of the case.
He said their time would be better spent preparing to fight the murder charges.
Democrat spokesman Chavanond Intarakomalyasut said Pathum Thani police had arrested a man for leading a group of red-shirt supporters to disrupt Saturday's speeches.
After mobilising a number of red-shirts to block traffic in front of the university, Wuthipong "Ko Tee" Kotchathamakhun broke through a police barrier at the entrance to the private function, Mr Chavanond said.