Rebekah Brooks has told the phone-hacking trial she drove her news team "crazy" as she tried to decide whether to pay for information that revealed the MPs' expenses scandal.
The former editor of the Sun said a public official had offered the data at "a very big price tag".
But she spent "too long" considering it and the Daily Telegraph eventually ran with the story.
Mrs Brooks denies four charges including conspiracy to hack phones.
Mrs Brooks is one of seven defendants on trial - she denies four charges including conspiracy to hack phones and to commit misconduct in public office.
Talking about the MPs' expenses story, she told the Old Bailey: "In terms of errors of judgement it was quite high on my list".
Mrs Brooks said: "Quite rightly the Daily Telegraph did it. The Met and CPS (Crown Prosecution Service) put out a statement saying they would not investigate because of the high level of public interest.
"It was quite embarrassing that we didn't do it."
"I thought about it for too long," she told the court.
"Days would go by and I thought, 'absolutely, go for it'. Then I would change my mind.
"I drove my news team crazy with my indecision. I should have gone ahead."
Earlier, Mrs Brooks was questioned about emails she received from reporters seeking permission to make anonymous payments to police officers and other public officials.
One reporter asked for money partly to "smooth the path" of a story he was working on about a woman who allegedly hired a hit man.
Mrs Brooks was asked to pay £1,000 to a serving police officer for a "wife-swapping" story and another £1,000 for "the first pic of cop killer Steven Graham".
Mrs Brooks confirmed she agreed a payment in 1998 to a naval officer in return for information that led to the headline "Saddam's Anthrax in our Duty Frees", which revealed concerns about the former Iraqi leader's plan to smuggle the disease into the UK.
She said the payment was in the public interest but the source was identified and prosecuted.
In the witness box for her sixth day of evidence, Mrs Brooks described being summoned to Downing Street over the leaked anthrax information.
'Right to know'
She said she met representatives from MI5, MI6, GCHQ and lawyers who asked her not to publish the story.
"It was a very brief discussion. The public had a right to know," Mrs Brooks said.
"There had been an all-ports warning. We discussed what not to run, ie what part of the operation could put any operatives in danger, but the very essence of the story we negotiated to run."
She said when she returned from the meeting, she authorised for money to be paid to the public official who leaked the information.
Mrs Brooks told the jury on Thursday that she approved payments to public officials - but only when there was an "overwhelming public interest".
The case was adjourned until Monday.