The Guardian has apologised to The Sun fora front page report on Tuesday which stated that the paper had accessed the medical records of the infant son of former prime minister Gordon Brown.
In a correction published on page 36 of today's paper, The Guardian admitted the mistake and apologised for the error.
The Sun is now pursuing other news organisations which ran the story. The allegation that The Sun had hacked the medical records of Gordon Brown's infant son Fraser in 2006 led the news agenda and looked like being nearly as damaging for The Sun as allegations about the hacking of murdered schoolgirl Milly Dowler's voicemails were for the News of the World the previous week.
Yesterday The Sun revealed that it found out Fraser had cystic fibrosis from a member of the public whose son also suffered from the condition.
The Sun said that it approached Mr Brown who gave his consent to publishing a story. After being contacted by The Sun, Mr Brown put out a statement about the matter leading to it being widely reported in The Sun and elsewhere the following day.
A spokesman for The Sun said that the Guardian story was "deplorable" and was part of a "an obvious attempt to discredit The Sun".
He said: "They should be ashamed of themselves. Mr Brown was very co-operative at the time of the original story and was keen to be a friend of The Sun."
Referring to the allegations made by Mr Brown, the spokesperson said: "It was unbecoming for a former prime minister to stoop so low".
The Guardian story has now been amended online, but it originally stated: "details of his [Brown's] infant son's medical records were obtained by The Sun".
Following yesterday's denial by The Sun, and its production of a sworn affadavit from its source for the story, a Guardian spokesperson said: "The Guardian report on News International targeting Gordon Brown stated that 'details from his infant son's medical records were obtained by the Sun, who published a story about the child's serious illness'.
"We did not specify who obtained the private information or how it was passed to the Sun, but their decision to publish the story clearly caused Gordon Brown and his family considerable distress."
Today, The Guardian said in its corrections and clarifications column: "Articles in the Guardian of Tuesday 12 July incorrectly reported that the Sun newspaper had obtained information on the medical condition of Gordon Brown's son from his medical records. In fact the information came from a different source and the Guardian apologises for its error."
Press Gazette understands that The Sun now plans to go on "the offensive" and seek further clarifications from other news organisations which ran the story.
Sun insiders were furious about the front pages of the Metro, Daily Mail and Telegraph in particular.
The Metro front page stated: "Brown's sick babies targeted by hackers"; the Mail front page said: "Gordon's baby was targeted" and the Daily Telegraph splash read: "My son's medical records were hacked, says Brown."
Press Gazette asked The Guardian about the relative size and position of today's apology, compared to the original front-page piece, a spokesperson said: "The Sun's complaint to the Guardian was dealt with in the usual way by our independent readers' editor. An apology was printed at the top of our daily corrections and clarifications column, which sits alongside the leader column and at the heart of the newspaper. This is where all corrections and clarifications have been published each day since the readers' editor's office was established 14 years ago and is where our readers expect to see it."