Pheu Thai says a political conspiracy has been launched to unseat caretaker Prime Minister Yingluck Shinawatra, citing the national anti-graft body's refusal to hear from more government witnesses.
The National Anti-Corruption Commission (NACC) faces the prime minister in a rice showdown, with most analysts expecting to see Ms Yingluck forced from office.
The National Anti-Corruption Commission rejected Ms Yingluck's request for extra witnesses to defend her oversight of the rice-pledging scheme, one of two cases which could remove her from power if adverse findings are made.
Caretaker Deputy Prime Minister Phongthep Thepkanchana Saturday questioned why the NACC had rejected the request.
"Allowing two more witnesses to testify will not take much time and will give the NACC more information in addition to the testimony by [Deputy Prime Minister] Kittiratt [Na-Ranong], who is a political officer while the additional two witnesses are civil servants," he said.
Key Pheu Thai Party figures also said the anti-graft body and Constitutional Court had been "hasty" in dealing with the cases against the caretaker premier.
The NACC is expected decide next month on whether Ms Yingluck was derelict in her duty. The Constitutional Court is also considering Ms Yingluck's role in the transfer of National Security Council secretary-general Thawil Pliensri in 2011, which a lower court overturned.
Mr Kittiratt was the government's final witness on Friday — the same day the NACC rejected Ms Yingluck's request to have two more witnesses testify on her behalf.
Ms Yingluck's lawyer asked the anti-graft agency on April 11 to allow cabinet secretary-general Ampon Kitti-ampon and Fiscal Policy Office director-general Somchai Sajjapongse to testify before the agency to complete her defence.
Mr Phongthep said Saturday that the two additional witnesses could have completed their testimony in one day.
If indicted, she will be required to suspend her duties as prime minister and the NACC will forward the case to the Senate, to carry out impeachment proceedings against Ms Yingluck.
Caretaker Education Minister Chaturon Chaisaeng criticised the charter court's strong reaction to the Centre for the Administration of Peace and Order (Capo), after the centre made a statement warning the court and the NACC against double standards in their handling of cases against Ms Yingluck.
Capo has also urged the caretaker government to seek His Majesty the King's advice if the charter court rules to disqualify Ms Yingluck and her cabinet.
Mr Chaturon said Capo was just trying to reflect concerns about the court's attitude and its handling of the case, which could have an impact on national security and peace. He said Capo's statement was not a threat, but intended as a warning against possible problems.
Science and Technology Minister and Pheu Thai legal adviser Phiraphan Phalusuk accused the charter court and the Election Commission of working together to delay a plan to hold a fresh general election until the end of July so there will be more time for the court to disqualify Ms Yingluck and her cabinet.
Key United Front for Democracy against Dictatorship leader Tida Tawornseth said the UDD would prepare for a major rally in the next few weeks to pressure the EC to call a fresh election as quickly as possible and prevent efforts to install an appointed government.
Ms Tida said the UDD would not wait until July for a fresh poll, as proposed by EC member Somchai Srisuthiyakorn.
Deputy Democrat Party leader Ong-art Klampaibul said he believed the charter and the NACC will rule fairly.
He added that efforts to delay the convening of a Senate meeting to discuss impeachment petitions against political office holders must be halted. Mr Ong-art called on Ms Yingluck to submit to scrutiny, adding that the government and Pheu Thai should stop clinging to power.
The NACC has asked the senate to impeach former speaker Nikhom Wairatpanich and former House Speaker Somsak Kiatsuranon, who are among 383 former politician who last year voted to make the Senate a fully elected chamber. The Constitutional Court ruled the amendment violated the charter.