The Democrats are working hand in glove with anti-government protesters and certain independent agencies under the constitution to topple the caretaker administration, the Pheu Thai Party says.
The allegation was countered by the Democrats which described it as a fabrication to justify Pheu Thai clinging to power.
In a renewed war of words, Pheu Thai legal expert and strategist Bhokin Bhalakula alleged the military was now being pressured by the Democrats, protesters and the independent agencies to stage a coup.
If the military refuses to act, the group would stir up a situation that would force the appointment of an unelected interim prime minister, according to a statement read by Mr Bhokin.
Mr Bhokin did not make any direct reference to any agency but it is understood he was referring to the Constitutional Court and the National Anti-Corruption Commission.
The judges ousted Ms Yingluck and nine cabinet members from their posts last week for abuse of authority in transferring Thawil Pliensri as National Security Council secretary-general.
The NACC, meanwhile, also decided to ask the Senate to impeach Ms Yingluck over alleged dereliction of duty in the rice-pledging scheme.
"These rulings are against the principles of the law and they have been handed down in a rush,” Mr Bhokin said.
The removal of Ms Yingluck and some of her cabinet members is part of a plot to appoint a new premier, Mr Bhokin said.
He warned the attempt would be futile as it went against democratic principles.
He called on the Election Commission to go ahead with the plan to organise a fresh election on July 20.
Responding to the Pheu Thai allegation, Chavanond Intarakomalyasut said Pheu Thai's repeated call for elections raises questions over what true democracy is.
He said Pheu Thai politicians keep talking about democracy but their minds are dictatorial.