Bailey is expected to depart at the end of the year and the newspaper group, which publishes the Mirror, Sunday Mirror and more than 100 regional titles, is now publicly searching for her successor.
Trinity Mirror says in a statement: “Despite the challenging environment the actions she has taken, together with the team, have ensured the company has consistently delivered robust profits.
“Importantly, Sly has also established the basis of a digital strategy for the group going forward.”
Bailey says her role was “fascinating and all consuming” but adds she feels the time has come for her to seek new opportunities elsewhere.
Trinity Mirror reported a 40% drop in profit to £74.4m for the full 2011 financial year. Revenue declined 2% to £746.6m in the period.