James Harding, editor of The Times newspaper, has admitted he "sorely regrets" the intrusion by his publication into the identity of a blog author known as NightJack.
"On behalf of the newspaper, I apologise," said Harding at the Leveson Inquiry, before adding "expect better of The Times and so do I."
The broadsheet editor was speaking for a second time at the investigation into press standards after he was recalled to give evidence.
Questioned over details surrounding the actions of reporter Patrick Foster who wanted to identify the author of a now infamous NightJack blog. Foster accessed the blogger's email account.
Foster had emailed the home news editor asking for a meeting "away from the desk" so he could discuss the matter.
Harding, who says he only found out about this process last week, told the inquiry: "If Mr Foster had come to me and said he had done this I would have taken the disciplinary action.
"I would have told him to abandon the story. And I squarely do not approve of what has happened."