Blair's contact with Rebekah Brooks was revealed Wednesday in an email read by prosecutor Andrew Edis, the Guardian reported.
The July 11, 2011, email, from Brooks to James Murdoch, then executive chairman of News International, recounted an hour-long telephone conversation Brooks had with Blair.
She wrote that Blair advised her to set up an "independent" investigation, and that he suggested the former director of public prosecution, Ken Macdonald, could be her "outside counsel."
Blair also advised her to "tough up" and "keep strong" and not make any "rash short-term solutions as they only give you long-term headaches."
He also said he was available to her and Murdoch as an "unofficial adviser."
Edis read the email to the jury as he wrapped up the prosecution's case against Brooks and five others.
Outcries following allegations of News of the World's extensive phone hacking resulted in the newspaper's closure July 7, 2011. Brooks was arrested six days after her conversation with Blair. At the time, she was chief executive officer of News International. She was editor of News of the World from 2000 to 2003.