An NHS chief has reportedly apologised to Labour's health spokesman after the Conservatives used a report he wrote to attack the previous government.
There have been angry clashes between the Tories and Labour over culpability for high death rates at 14 health trusts.
Labour dismissed the attack as a "smear campaign".
Now The Observer is claiming Keogh has apologised to Burnham about the way his report was used.
Tories had briefed that the report revealed 13,000 patients needlessly died, but Keogh said he did not recognised the figure.
According to The Observer, when Keogh and Burnham met recently, Keogh was overheard saying "Andy, I'm so sorry", while Burnham was said the NHS chief had "nothing to apologise for".
The paper also claimed Keogh had sent emails to "an unnamed individual" saying: "Don't believe everything you read, particularly in some newspapers."