The Guardian has apologised to The Sun after it made claims about the tabloid obtaining the medical records of Gordon Brown's son.
The newspaper said The Sun accessed the Brown family's medical files without their knowledge to find that the former prime minister's son Fraser had cystic fibrosis.
The information led the tabloid to publish an article in November 2006 revealing that the four-month-old had the condition, The Guardian said.
However, The Sun, which is owned by Rupert Murdoch's News International, denied the claim, insisting its source had been a member of the public.
It said an unnamed man, whose child also suffered from cystic fibrosis, contacted its journalists with the information in the hope it would raise awareness about the condition.
The newspaper said the individual had signed a legal affidavit confirming this.
In a statement printed in its corrections and clarification section today, The Guardian said: "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."
A spokesman for The Sun criticised The Guardian for running the story and praised its own journalists for bringing its readers "agenda-leading news stories, with legitimate news gathering techniques".