The official has got himself in hot water over an e-mail he supposedly sent to Nedum Onuoha’s mother, who is also his agent, ridiculing her medical condition.
Dr Anthonia Ohuoha has been diagnosed with cancer, and stated receiving the e-mail from Cook was worse than actually having the disease.
The Eastlands outfit pledged to look into the incident, and following their investigations Cook has decided to leave his post.
“I am privileged to have held my position at Manchester City football club and to have experienced the opportunities that it has presented,” Cook told reporters.
“It is that factor, together with my error of judgement in this matter that has prompted me to reach this decision, which I believe is in the best interests of the football club. I wish Roberto and his team and all of the fans and supportive partners of the club the very best for exciting times ahead,” he concluded.
Meanwhile, chairman Khaldoon Al Mubarak thanked Cook for his efforts over the last number of years.
“Garry has made a remarkable contribution to Manchester City football club over the past three years,” he told the club’s official website.
“His judgement in this matter should in no way lead to his accomplishments being overlooked. On every level, the club is unrecognisable from the organisation which he inherited and our staff and supporter services, community outreach and commercial activity have seen unparalleled growth under his direction with yet more projects to be realised on the horizon.
“On behalf of Sheikh Mansour and the board, I would like to thank him for his energy and tireless commitment to serving all those connected with the football club. He will always be welcome at Manchester City,” the statement read.
Director John MacBeath has been instilled as a temporary CEO whilst the Premier League outfit look for Cook’s replacement.