Mr Yongyuth's eligibility to serve in the cabinet and as an MP is in doubt since the National Anti-Corruption Commission (NACC) found him guilty of malfeasance for his handling of the controversial Alpine land case while he was a deputy permanent secretary for the interior in 2002.
The Interior Ministry's Civil Service Committee has decided to expel Mr Yongyuth with the expulsion order retroactively taking effect on Sept 30, 2002.
However, the committee has claimed that the expulsion, which was imposed this Sept 14, is also retroactively overruled by the 2007 Exoneration Act.
A source in the Pheu Thai Party said that Mr Yongyuth faces mounting pressure within the party despite support from Prime Minister Yingluck Shinawatra.
Mr Yongyuth has received a direct order from "those in power" to suspend his duties pending a final ruling on his status, the source said.
His absence from the cabinet meeting on Tuesday has fuelled suspicions that his job is at risk. He reportedly opted to inspect the flood situation in Prachin Buri instead.
Mr Yongyuth has been assigned to serve as acting prime minister during Ms Yingluck's visit to the US.
This may explain the Pheu Thai Party's petition submitted to the Election Commission (EC) asking the agency to rule on Mr Yongyuth's eligibility to hold political office. The hand-written petition was submitted by Pheu Thai spokesman Prompong Nopparit.
The source said that certain groups of red shirts, apparently backed by MPs jockeying for a cabinet seat, are stepping up pressure on Mr Yongyuth. Red shirts from Surin led by Thepphanom Namlee have already petitioned the EC to rule on Mr Yongyuth's status. Others are pressuring him to resign to avoid the possible dissolution of the party if Mr Yongyuth is ultimately found culpable and forced from office, as he is also the Pheu Thai leader.
The call for his resignation comes despite the Council of State's reaffirmation that Mr Yongyuth is covered by the 2007 Exoneration Act.
Democrat MP for Songkhla Wirat Kalyasiri said yesterday that the deputy prime minister is being forced by his own party to take the fall.
His opponents say that leniency under the exoneration act is not possible until Mr Yongyuth has served his punishment.
"He is being ousted by those who have the real power in Pheu Thai. They want to put an end to the Alpine case which is linked to other [politicians]," Mr Wirat said.
Mr Yongyuth had approved the sale and ownership of plots of land in Pathum Thani to Alpine Real Estate and Alpine Golf and Sports Club in 2002 despite the Council of State's ruling that it was monastic land and thus could not be sold or transferred.
The real estate developer had connections with former deputy interior minister Sanoh Thienthong and the property was later sold to former prime minister Thaksin Shinawatra.
Mr Wirat said that Pheu Thai's petition to the EC for a ruling is nothing but an attempt to buy time.
"He thinks he may be able to clear the mess. If he really believes he is an eligible MP, why doesn't he ask the Constitution Court to make a ruling? It will go to the court sooner or later," the Songkhla MP said.
The Democrat Party is collecting signatures of 50 MPs to endorse a petition seeking a Constitution Court ruling on Mr Yongyuth's status. The petition will be submitted by the House Speaker.
Mr Wirat said the House Speaker is required to forward the petition to the charter court within 15 days.
A ruling would be expected in three months, he added.
Pheu Thai MP and legal specialist Pirapan Palusuk said yesterday the petition to the EC would clear any doubt about the party leader's qualifications.
He said it is the right authority to consult when the Council of State and the NACC seem to disagree.
Mr Pirapan added it was unlikely that Mr Yongyuth would lose his post _ especially with Ms Yingluck's support.
"Most party members don't think he has done any damage to the party. I don't think it will make a significant impact," he said.
Jaturan Boonbenrat, assistant coordinator for the Green Politics Group, said the group has asked the EC to rule on the qualification of Science and Technology Minister Plodprasop Suraswadi in addition to Mr Yongyuth.
Mr Plodprasop was found guilty by the NACC of malfeasance over the export of 100 Bengal tigers to a Chinese zoo when he was chief of the Royal Forest Department.