BANGKOK: Thailand's election-winning Move Forward Party will not back former alliance partner Pheu Thai's candidate in a parliamentary vote on the next prime minister, a senior official said Tuesday.

The decision by Move Forward, which has the most seats in parliament, could complicate efforts by political heavyweight Pheu Thai to get the required support to form a government, and prolong weeks of political deadlock.

Despite abandoning Move Forward earlier this month, second-placed Pheu Thai has sought its backing for former real estate tycoon and political newcomer Srettha Thavisin to become premier.

Move Forward's lawmakers were unanimous in opposing that, its secretary general, Chaithawat Tulathon, told a news conference.

"The formation of government now is not reflective of the people's voice," Chaithawat said.

"It is clear senators and other parties want to shut Move Forward down."

Thailand has been under a caretaker government for the past five months and the next parliamentary vote on a prime minister has yet to be scheduled.