Gary Cook, the chief executive of Manchester City Football Club, has resigned after he was accused of making fun of one of his player's mothers for having cancer.

Cook was alleged to have mistakenly sent an insensitive email to one of his players mothers that was intended to be received by the club's director of football Brian Marwood.

Instead it was sent to Dr Anthonia Onuoha, who acts as an agent for her son, Nedum Onuoha.

The offending email came after Dr Onuoha informed Man City that while she was "ravaged with cancer" it would not prevent her from negotiating on her son's behalf.

She later received an email from Cook addressed to "Brian" that read: "Ravaged with it!!........I don't know how you sleep at night. You used to be such a nice man when I worked with you at Nike. G".

Cook had denied sending the email and claimed his account had been hacked.

In a statement issued on Friday afternoon Man City said "there is foundation to Dr Onuoha’s allegations" and said the chairman, Khaldoon Al Mubarak, had written to apologise to Dr Onuoha for any distress caused.

The club added: "Following the findings of the review, Chief Executive Officer Garry Cook has offered his resignation, which has been accepted with regret by the Board."

Cook has admitted to making an "error of judgement" and said that his resignation was in the best interests of the club.

“I am privileged to have held my position at Manchester City Football Club and to have experienced the opportunities that it has presented," he said.

"The privilege is in part offset however by the significant personal focus which has at times, detracted from the magnificent achievements of those working at the football club.

“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."

The club's chairman Khaldoon Al Mubarak said the incident should not overshadow Cook's achievements at the helm of the club.

"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," he said.

“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 club's director John MacBeath will step into fill cook's role until a replacement is found.