Bo Xilai has accused his ex-police chief Wang Lijun of lying over allegations of abuse of power.
Disgraced Chinese politician Bo Xilai launched a scathing attack on Wang Lijun, his former associate in the central city of Chongqing, saying his testimony was “full of lies and fraud”.
The trial, in its fourth day in the city on Jinan, was later adjourned until Monday.
Bo Xilai, a former Communist Party chief in Chongqing, denies wrongdoing.
The scandals involving Bo Xilai’s family have captivated the country.
Many analysts assume the outcome of the trial has been predetermined with a guilty verdict, however, observers say Bo Xilai has put up a spirited defense.
Foreign media are not allowed into the trial, but the court in the eastern city of Jinan has been posting regular updates on China’s micro-blogging site Weibo (in Mandarin).
On Saturday the trial focused on accusations that Bo Xilai covered up the murder of British businessman Neil Heywood in 2011.
Bo Xilai’s wife, Gu Kailai, has already been convicted of murdering Neil Heywood.
Wang Lijun had been a key figure in court on Saturday, testifying that Bo Xilai had punched him after he told the politician his wife was responsible for the death of Neil Heywood
But Bo Xilai told the court on Sunday: “His character is extremely bad, he created rumors… and threw dust in the public’s eyes.
“It’s beneath legal credibility to present such a person as a key witness. Wang Lijun was lying during the trial and his testimony was not valid at all. His testimony was full of lies and fraud.”
He added: “He said I hit him with my fist instead of slapping him in the face. But the truth is I never learned the technique of Chinese boxing so I wouldn’t be able to have that power.”
On Saturday, Bo Xilai acknowledged he made “serious errors of judgement” but that the charges against him were “exaggerated”.
The abuse of office charge stems from accusations that Bo Xilai knew and covered up the fact that his wife murdered Neil Heywood.
Bo Xilai told the court he had discussed the accusations with her, and his wife told him that she was being framed for the murder.
He also described two difficult meetings he had with Wang Lijun on 28 and 29 January 2012.
Days after this confrontation, Wang Lijun fled to a US consulate to seek asylum, and the scandal became public knowledge.
Wang Lijun has already stood trial for his own actions and been jailed for 15 years, for defection, power abuse and bribe-taking.
Gu Kailai has also testified against her husband. On Friday, Bo Xilai described his wife as “insane” because she had implicated him in corruption.
She claimed that wealthy Chinese entrepreneur Xu Ming bought gifts for the family in order to gain favors.
Bo Xilai is also accused of embezzling 5 million yuan ($800,000) in 2000 which had been earmarked for a construction project in Dalian. Bo Xilai was the city’s mayor in the 1990s.
But at Saturday’s hearing Bo Xilai blamed his wife Gu Kailai for this, saying he had no knowledge that she had taken the money until later on.