Pheu Thai Party members have expressed concern at suggestions that Thaksin Shinawatra's younger sister Yaowapa Wongsawat could be groomed to take over as premier.
Sources said the members felt such a move, should Prime Minister Yingluck Shinawatra be forced from office, would do the party more harm than good.
It's believed senior party members had tipped Mrs Yaowapa to take over in case Ms Yingluck is disqualified over a loan transaction probe by the National Anti-Corruption Commission (NACC).
Speculation about Mrs Yaowapa began after her close aide Kasem Nimmonrat abruptly resigned as a Chiang Mai MP.
The Pheu Thai source said Mr Kasem's resignation was to allow for Mrs Yaowapa to contest the resulting by-election.
The source said senior party members had concluded they needed someone to be ready to replace Ms Yingluck.
"Our pu yai [senior figures] received some information that there may be a political shake-up in the next few months that might adversely affect Ms Yingluck's premiership status," said the source.
"So by getting Mrs Yaowapa elected as an MP is a precaution."
Ms Yingluck is being investigated by the NACC over allegations she lent 30 million baht to a company in which her spouse, Anusorn Amornchat, was a shareholder.
The NACC is looking at whether asset concealment was involved.
The source said it was felt having Mrs Yaowapa on standby might not be a good idea. Unlike Ms Yingluck, who was not involved in politics before the last election, Mrs Yaowapa's public image is as a core political broker and leader of Pheu Thai's large faction of northern MPs.
Her image is likely to upset Thaksin's critics and neutral groups.
Mrs Yaowapa's rise to power would make the ruling party an easy target, possibly undermining the government's stability, said the source.
Several Pheu Thai MPs were caught off guard by the speculation. Some doubted that Mrs Yaowapa would be a smart choice.
Somkid Chuekhong, a Pheu Thai MP for Ubon Ratchathani, said it could be inappropriate to have Mrs Yaowapa succeed Ms Yingluck.
A political observer in the North said Mrs Yaowapa did not fit the image of a national leader.
Pheu Thai is expected to hold a press conference on the issue today.