He revealed his decision on Friday, the day after the Post’s parent company Trinity Mirror announced it was putting 19 jobs at risk of redundancy in its Birmingham newsroom and a further six in Coventry.
Stacey’s position was not thought to be among those at risk and no date has yet been set for his departure.
During his time at the Post, he was responsible for launching the paper’s app and more than doubled its online audience in one year.
He also spearhead its ‘Hidden Spaces’ project, aimed at promoting rarely-seen Birmingham buildings through photographic supplements.
“He was pivotal in the Mail’s evolution into an award-winning digital title, leading digital developments here when he was executive editor.
“As editor of the Birmingham Post, he took the title even further on the digital journey, launching the Birmingham Post app and more than doubling its online audience in a year.”
He added: “He goes with our very best wishes and thanks for all he has achieved over a great many years.”
This was followed by a five-year spell on Trinity Mirror’s magazines division as design editor and then editor-in-chief, overseeing a portfolio of lifestyle and entertainments magazines and contract-published titles.
Stacey joined the Birmingham Mail as assistant editor in 2005 and was appointed executive editor three years later with a brief to help increase the newspaper’s digital readership.
He took up his current role in February 2013 , succeedingAlun Thorne in the editor’s chair.