Democrat Party executives are being urged to find a way to curb defections that are causing internal instability, the party's MP for Trang Sathit Wongnongtoey said.
However, he added, party executives must first acknowledge that there is a problem.
"We need to face up to reality, though it may be painful to accept," he said.
Mr Sathit, himself a former Democrat executive and former PM's Office minister, insisted the present executives must act fast to rectify the problem.
He said the party suffered a hard blow with the exit of former finance minister Korn Chatikavanij, who also previously served as deputy Democrat leader. Shortly after Mr Korn quit, another veteran Democrat, Atthawit Suwannapakdi, walked out.
Mr Korn left the Democrats to set up his own party, "Kla" (Dare), with Mr Atthawit one of the reported members.
This week, five Democrats holding posts at the Bangkok City Council and Bangkok district councils defected to the rival Pheu Thai Party.
Among the defectors, Prasert Thongnoon, a former Bangkok city councillor, said he and the others had turned their backs on the Democrats because the party had broken its promise by joining the Palang Pra-charath Party-led coalition, which is accused of supporting the legacy of coup-makers.
Mr Sathit said yesterday the departures are symptomatic of problems that exist within the party, and it is the duty of the executives to analyse and tackle them in order to keep the party united. "That will also boost the confidence of those who remain and those who will join in the future," he said.
Meanwhile, Democrat spokesman Ramet Rattanachaweng insisted supporters and members of the party had given it the mandate to join the coalition so it can push through its election policies.