Concerned by the reported plot, Bo asked the brother of his first wife Li Danyu to meet him at a government compound in the southwest metropolis of Chongqing, The New York Times reported.
Bo, 63, who was then the Communist Party chief of Chongqing, pointed to a stack of papers and said he had forensic reports that proved the existence of a plot to poison his second wife, Gu Kailai, it said.
The person suspected of masterminding the scheme, Bo said, was his son from his first marriage, Li Wangzhi, a graduate of Columbia University who was working in finance in Beijing, the paper reported.
"Could this be true?" Bo asked. When the brother-in-law insisted the fears were outlandish, Bo seemed relieved, it said.
The story, recounted in two recent interviews with Bo's estranged first wife, Li Danyu, 62, deepens the Shakespearean dimension of a scandal that has gripped China and disrupted the party's once-a-decade leadership transition, the report said.
Until his downfall, Bo was considered a contender for a top post during the handover of power that is taking place from November 8. But those hopes were dashed when he was detained.
On September 28, the CPC announced it had expelled Bo and allowed his prosecution on a range of criminal charges. His second wife, Gu, 53, has been convicted of murdering a British businessman, Neil Heywood last November.
In the interviews, Li, also a "princeling" child of a party official, said that although there has been a long history of enmity between her and Gu, her son never conspired to murder Gu.
Although she has no proof, Li said she suspected Gu was the one who first blamed her son for the perceived murder plot, and the so-called forensic evidence might have been provided by Wang Lijun, the former police chief convicted of helping cover up Heywood's murder. Li said she feared Gu wanted to have her first son arrested or harmed.
"She can be that paranoid," Li said. As for Bo, she said, he was "good in nature and didn't want to believe this evidence."
