The former wife of ex-cabinet minister Chris Huhne blamed their break-up on his "sexuality" and past relationships with men, a jury has heard.
Part-time judge Constance Briscoe, who is accused of lying to police about the couple's speeding points case, claimed Vicky Pryce had believed her husband was engaged in "that activity again".
Southwark Crown Court also heard claims Mr Huhne was punched by his ex-wife.
Ms Briscoe denies intending to pervert the course of justice.
Giving evidence, Ms Briscoe, 56, told the court Ms Pryce had wanted to tell the press about her husband's sexuality.
"She wanted to discuss the fact that Chris had relations with men before they got married and also wanted to discuss how he had infected her with an STD [sexually transmitted disease] when he was a European MP, and when she confronted him at the time he said he got it from clean sheets," Ms Briscoe said.
"She felt extremely bitter about the marriage break-up and she felt that the reason why the marriage had broken up was because of Chris and, can I say, his sexuality.
"She believed that the reason why the marriage had broken down was because Chris, her husband, had been engaging in that activity again."
Ms Briscoe also claimed her friend and next-door neighbour Ms Pryce had told her that she had taken her "eye off the ball" in relation to her husband and his aide, Carina Trimingham, with whom he had started a relationship.
"She was cross with Miss Trimingham but she was more furious with Chris because he had conducted a campaign on family values at the time he had that affair with Miss Trimingham," Ms Briscoe said.
She went on to tell the court that on one occasion, when Mr Huhne visited the family home after the split in 2010, Ms Pryce attacked him.
"She dragged him through a window and punched him a few times on the eye," she said.
Mr Huhne had to wear make-up during later TV appearances to hide a black eye, she added.
Jurors also heard claims that Ms Pryce became convinced Mr Huhne had bugged the house and was intercepting her emails.
Ms Briscoe said she knew Ms Pryce had agreed to accept speeding points on Mr Huhne's behalf in 2003 and advised Ms Pryce to "come clean to the relevant authorities".
"After this I saw Vicky driving Chris around and assumed that it had been sorted out and he had come clean," she told the court.
But after they split up, Ms Briscoe said she thought it was in the public interest to report the speeding points case as Mr Huhne showed ambitions to be deputy prime minister.
"I thought he was a hypocrite," she told jurors.
After Ms Pryce's break-up, Ms Briscoe advised her to go to the press because it would be "good therapy", she told the court.
Earlier on Monday, the court was played a police interview with Ms Briscoe, in which she told an officer she had never wanted "to get involved in the first place" with the couple's speeding points case.
In the recording she was heard saying: "I'm livid. I didn't even want to get involved in this wretched incident in the first place.
"At the end of the day, Vicky Pryce and Chris Huhne know what happened and I don't.
"I have got no idea what went on in 2003 and all of a sudden I'm the one.... Perjury for heaven's sake. I'm bloody not happy about it at all."
She added: "I was merely the contact for the Mail on Sunday to provide assurances to her [Ms Pryce]."
Ms Briscoe, a part-time judge and a barrister, has been suspended since her arrest in October 2012.
She is alleged to have provided police with two inaccurate statements about her role as an intermediary between Ms Pryce and reporters, produced an altered copy of a statement, and got a document expert to view the wrong version of the statement.
She denies three counts of intending to pervert the course of justice.
Former Energy Secretary Mr Huhne was jailed in March last year after admitting perverting the course of justice.
His ex-wife, economist Ms Pryce, was also jailed after a trial for the same offence. Both have since been released from prison.
The trial continues.