The eight-party alliance seeking to form Thailand's next government proposed Move Forward leader Pita Limjaroenrat as their candidate for prime minister as the joint sitting of parliament began on Wednesday.
It is his second attempt to win the endorsement of the bicameral legislature after losing in his first attempt last Thursday.
Pheu Thai renominated Pita to parliament at 9.38am.
The United Thai Nation Party immediately argued against it, citing parliamentary regulations prohibiting a failed motion being resubmitted at the same session.
Key members of the Move Forward Party insisted on the legality of the renomination of Mr Pita.
MFP won the May 14 general election with 151 House seats while the Pheu Thai Party came second with 141. they are the key parties in the eight-party alliance.
Key Pheu Thai figures recently commented that the renomination of Mr Pita could not continue forever because people were anxious for a new government to be formed and tackle national issues.
Pheu Thai also announced that Srettha Thavisin, one of its prime ministerial candidates, would be nominated for prime minister if Mr Pita was rejected again.
Mr Pita earlier promised to make way for Pheu Thai unless he won at least 10% more votes than he obtained in the first round of the prime ministerial vote on July 13.