Stuart Hoare said his younger brother, who died of alcoholic liver disease in July, worked at both newspapers before his death, The Guardian reported.
In testimony before the Leveson inquiry, a government panel investigating media ethics in Britain, Stuart Hoare said his brother had claimed in e-mails that phone hacking was "routine at The Sun" and "probably more daily at the News of the World."
"Sean had worked with certain individuals at both The Sun and News International where phone hacking was a daily routine," Hoare said in a written witness statement. "The reality was that phone hacking was endemic within the News International group [specifically Sean identified that this process was initiated at The Sun and later transferred to the News of the World] and he went on record both verbally and in writing to make this claim."
His brother eventually talked to The New York Times about the phone hacking. The U.S. newspaper published Sean Hoare's allegations in September 2010.
"Sean's decision to go public certainly wasn't motivated by money as he did not get a single penny for any of the articles written in The New York Times. His sole motivation was based on trying to put wrongs right," Hoare wrote in his witness statement.