Stories for which the Sun paid a civil servant thousands of pounds could have come from a variety of legitimate sources rather than a public official, the paper's former editor Rebekah Brooks said today.

Giving evidence at the phone hacking trial, Mrs Brooks explained that although she had approved a reporter's requests for payments of £40,000 for military exclusives, she was unaware that the source was a Ministry of Defence official, Bettina Jordan-Barber.

Mrs Brooks's counsel, Jonathan Laidlaw QC, asked her to review the articles and consider their possible origins.

Scanning a story headlined "Army girl hid baby while in barracks", published on page 7 of the Sun on 3 March 2009, Mrs Brooks said there was "no" indication it had originated from a public official.

She told the Old Bailey: "Clearly there is an an Army source [quoted in the article]... obviously I would have read it as an Army source, well - someone who works in the army, but that wouldn't necessarily flag up payment to a public official."

Had she known the source was a public official, she would not have sanctioned the payment, she said.

Asked about another story - "Married colonel faces boot for Afghan fling" published in the Sun on page 19 on 7 March 2009 - Mrs Brooks said: "There is the MoD confirmation of the story but the original tip could have come from the embassy, it would have come from Kabul... it could have come from a variety of sources, including wives."

On another story published in 2009, about a cadet being sacked for a relationship and headlined "The Lust Post," she said: "Part of it, obviously, has come from inside [the Army] because there's a quote there..." but added the whole point of confidential sources was that they were not revealed in stories.

She said that the reporter who requested the payments "had contacts everywhere," adding: "Nothing had been brought to my attention. The Sun publishes 100,000 stories a year. I approved it, I probably thought: 'Well done'. I'm surprised at my lack of congratulations [in her response to the request for payment] but I was so busy."

Mrs Brooks denies conspiracy to hack phones, conspiracy to commit misconduct in public office and conspiracy to pervert the course of justice.