Former Cabinet minister Chris Huhne transferred his speeding points to his wife without telling her, a court has heard.
A political journalist said Vicky Pryce had been pressured into taking the fine, and was presented with a "fait accompli" by her husband.
Pryce denies perverting the course of justice.
Isabel Oakeshott, political editor of The Sunday Times, first met Pryce by chance at the Liberal Democrat party conference in 2010, shortly after her marriage to Huhne had broken down. She went on to work with the economist to get the story published.
Giving evidence at Pryce's trial at Southwark Crown Court today, Oakeshott said that as the pair discussed publishing the story in email conversations, it was clear to her that Pryce wanted to expose what she saw as her former husband's wrongdoing.
"Vicky was a very, very hurt woman and she was quite clear that she felt that Chris, her former husband, did not deserve to be in the position of immense responsibility that he had at that time," she said.
"I am very clear that she wanted to expose what she saw as his true character."
Oakeshott said that after meeting Pryce briefly at the party conference, she made arrangements to meet her for lunch.
"Vicky Pryce had been a senior government economist so she was interesting in her own right to me for her views on the economy," she said.
"Secondly, she was at that time still married, although their relationship had disintegrated, to a cabinet minister, so I was interested in her relationship to him and how it had broken down.
"I met her for lunch in early March and we talked a bit about the breakdown of her marriage and during that conversation she mentioned to me towards the end of the meal that she had taken speeding points on behalf of her husband, she had been pressured to do that.
"Obviously that's a very serious allegation against a serving Government minister."
She said Pryce had made the allegation "slightly under her breath", and did not go into details, but mentioned it had happened in 2003.
Oakeshott said Pryce was concerned about how the story might impact on her. "She is a high-flying, professional woman who is clever enough to always have in mind her own reputation, and my hope was to get her to talk openly about what had happened, no ducking or diving."
As she tried to get more details about the claims, Oakeshott said Pryce told her she had been pressurised by Huhne into taking the points.
"My understanding from her was that the first she knew that a speeding offence had been committed was that she received a letter through the post addressed to her saying that she had been nominated as the driver of the vehicle which belonged to her husband," she told the court.
She said Pryce said she was shocked to get the letter as she had not been driving the car and did not know the area where it had happened.
"My understanding was that they had had a row about it and she had confronted him and asked him why on earth she had received this letter," she said.
"He had filled the form out, nominated her without any consultation about it and put her in an extremely difficult position.
"She was understandably very upset about it.
"She did not seem to have a very detailed recollection of these circumstances but she was clear she had filled in the form herself, but had been very, very unhappy about doing so and felt that she had been put into an impossible situation by doing so, and that it had been a fait accompli.
"She was very clear that he had pressurised her into signing the form and the context of that was that he risked losing his licence at that point because he had already amassed so many penalty points and he very much needed to be able to drive for his job at that time.
"It had clearly been very unpleasant and difficult and upsetting for her."
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