She told the – which described the saga as “Shakespearean” – that months before Bo fell, he told her brother he had forensic evidence of a plot to kill Gu, his current wife.

Bo reportedly said the suspected mastermind was his own son with Li, Li Wangzhi who is also known as Brendan Li. He is a graduate of Columbia University and works in finance in Beijing.

The said Bo’s brother-in-law described the suspicions as outlandish and the politician appeared relieved.

Official accounts of Gu’s conviction for poisoning Briton Neil Heywood said she believed he was a threat to her own son Bo Guagua. She was given a suspended death sentence, which is normally commuted to life in prison.

The allegations against her became public earlier this year after Bo’s former key aide and Chongqing police chief Wang Lijun fled to a US consulate to seek asylum. They have since spiralled into the Communist Party’s worst scandal in decades.

State media said late last month that Bo had been expelled from the party and would be tried on charges including corruption and abuse of power.

It also announced that a key party congress, when a new generation of leaders will take over, would begin on November 8.

Bo was once seen as a top candidate for promotion to the party’s highest echelons of power. His fate and the congress date had been the subject of intense speculation over whether the scandal would unsettle the transition.

No date has so far been set for Bo’s trial.

Li and Bo met in 1975, towards the end of the Cultural Revolution. Their son was born in 1977 but their divorce was finalised in 1984.

The cited Li Xiaolin, a lawyer linked to Gu who is no relation to Bo’s first wife, as saying the family believed Gu was poisoned years ago using a heavy metal.

The lawyer did not immediately respond to requests for comment on Sunday.