Former ODM executive director Magerer Langat has threatened to release "unpalatable secrets" about the party and its leader Raila Odinga if former TNA secretary-general Onyango Oloo "continues to undermine Jubilee".
During a meeting to endorse Kenya Ports Authority director Fred Kirui for governor position in Kedowa, Kipkelion East Constituency, Mr Langat said the information he would release about the rot in the Orange Party would be sufficient to deny the opposition the support it needed to win the presidency.
"Nobody knows ODM and Raila like I do. I will release information that will destroy whatever support that party still enjoys," Mr Langat said.
"I heard that Oloo has threatened to spill the beans. He should know that I also have a damning dossier on ODM."
His threat comes two weeks after Mr Oloo -- who unexpectedly left Jubilee for ODM - said he would make public sensitive information that could damage the reputation of President Uhuru Kenyatta's party ahead of the August elections.
Mr Langat said Mr Odinga was not fit to be president "because he lacks policies to drive development and is only intent on attaining power for his interests".
"Jubilee has done a lot for this country and deserves another term," he added.
Mr Langat quit ODM at the end of 2014 following his eviction from the party's meeting by Nairobi County ward representatives.
He has also declared interest in the Kipkelion West seat, held by Mr Jackson Rop.
Mr Langat has promised to back whoever wins in the Jubilee nominations slated for April.
"I want my seat back now that I am in Jubilee. I ask Kipkelion West residents to support me and President Kenyatta," he said.
The two will battle out for the Jubilee ticket with Kenya Bureau of Standards director Hillary Kosgei, Mr Philip Mutai and Mr Thomas Cheruiyot.