The Sun's Whitehall editor today denied knowing she was committing a crime by paying an HMRC source for stories.
Clodagh Hartley told the Old Bailey: "I would not have risked going to prison for stories in The Sun."
The 40-year-old (pictured, Reuters) is accused of arranging payments of £17,475 to senior press officer Jonathan Hall over a period spanning more than three years, in exchange for tips.
She estimated that Hall's information had led to around 17 of "maybe" 500 stories she had written.
And Hartley condemned News International for handing over swathes of emails to the police and wrecking her "moral duty" to protect her source.
Hall, 43, convinced his girlfriend to let him use her account for receiving thousands of pounds from News International, it is alleged.
He is said to have arranged with Hartley to switch the payments to his partner Marta Bukarewicz's bank account, in a botched attempt to hide his tracks.
Both Hartley and Bukarewicz, 45, deny conspiracy to commit misconduct in public office.
Hartley continued to be cross-examined by prosecutor Zoe Johnson QC today.
Johnson began by insisting Hall was not a whistleblower, adding "paying him for information is just an example of lazy journalism".
Hartley said that "to me, he was a whistleblower".
She said that paying sources was normal practice at The Sun.
"It was part of the arena in which we operated and the public and people who came to use with information expected to be paid."
Johnson said Hartley's only aim had been to "steal a march" on rival newspapers.
The prosecutor said the leak of Budget details in 2010 by Hall "could never be described as whistleblowing".
Hartley replied: "I think it is in the public interest… I think it is whistleblowing."
Hartley said she had felt a responsibility to protect Hall's identity as a whistleblower.
"I had a moral duty that was taken away from me – the ability to protect a source."
Discussing an internal email in which Hartley told of having received "the entire Budget", she again admitted it was "an overbold claim".
Hartley told the court she had hoped to attract other sources, due to the potentially high-profile Budget scoop.
Johnson said: "There is a world of difference between MPs' expenses, which you keep coming back to, which was about criminality, and the leaking of the Budget. You are not comparing apples with apples."
The prosecutor added: "How is leaking the Budget exposing wrongdoing?"
Hartley replied: "In this instance, it is not to allow the government to always control the flow of information."
Johnson asked: "You know, don't you, that ignorance of the law is no defence?"
"I was told that to my horror after being arrested," Hartley replied.
"But I could not have known that this was offence because no journalist had ever been arrested or prosecuted under this Act, that I found out came in 1906."
She added she had "no inkling" she might be committing a crime.
Hartley went on to say that Hall initiated "99 per cent" of their conversations.
"I am not soliciting him, I am absolutely not soliciting him."
Johnson said: "This isn't Watergate. You knew that he [Hall] was doing something that he was not authorised to do?"
Hartley replied: "I didn't think in those terms – 'is Jonathan authorised to give me this?'.
"I thought can Jonathan give me something I can tangibly use – I did not for one second think: 'was he authorised?'."
Hartley maintained all her stories were "fully justifiable in the public interest".
Johnson suggested Hartley's comments were "predicated on 'we are all deceived by every organ of the state'".
Returning to the stressful environment in The Sun's political team, Hartley told jurors she was "terrified" of an "unpredictable" senior colleague, who cannot be named.
"He had been trying to force me out of my job. He had said very many incorrect things about me in my assessment."
Hartley said this was why she advised Hall to avoid too much contact with her senior colleague.
Johnson asked: "Are you suggesting he might reveal your source?"
"Yes. I was just very scared," she replied.
"Of all people, he was the last person I felt I could trust."
Johnson insisted this was unlikely, as the desire to protect sources was in the "bloodstream" of all journalists.
"I can't speak for what was in his bloodstream.
"He is unlike any other journalist I have ever met."
Johnson criticised Hartley for texting Hall about the alleged bankruptcy of Johnson Behari VC, because of The Sun's normal support for the armed forces.
Hartley said the angle of the story would have been: "How could a decorated war hero be allowed to go bankrupt".
She added she had been off work with stress, directly caused by the fractious relationship with the senior colleague.
Johnson asked if Hartley was aware that Hall's inquiries into a private citizen's tax affairs could be a criminal offence.
"No, I absolutely did not."
Hartley said she had made the inquiries as a favour to the news desk.
"You are right, I should have said 'I'm sorry, I'm not working,' I wish I had."
Concluding the cross-examination, Johnson said Hartley had helped corrupt Hall.
"I never felt I was corrupting him," she said.
"I never knew it was against the law.
"I would not have risked going to prison for stories in The Sun."
Alexandra Healy QC declined to re-examine her client.
Judge Rook asked Hartley if she could roughly indicate how many stories had come from Hall.
Hartley said: "This would have been maybe 17 out of hundreds of stories that I wrote – 500 maybe."
Both Hartley and Bukarewicz deny conspiracy to commit misconduct in public office.
Hall has accepted he supplied stories for which he was paid.
Bukarewicz, of Kentish Town, north London, and Hartley, of Brockley, southeast London, deny conspiring to commit misconduct in a public office.
Hartley's defence case continues.