The chief constable of Greater Manchester Police has resigned after the force was placed in special measures over its failure to record more than 80,000 crimes in the space of a year.
A report by the UK's Inspectorate of Constabulary and Fire and Rescue Services (HMICFRS) last week said it was "deeply troubled" by how cases handled by GMP were closed without proper investigation.
The watchdog also said the service from England's second largest police force to victims of crime was a "serious cause of concern".
Chief Constable Ian Hopkins said: "These are challenging times for Greater Manchester Police.
"The force has a long-term strategic plan to address the issues raised by the HMIC and I believe this plan should be led by a chief constable who can oversee it from start to finish.
"Considering what is best for GMP and the communities we serve, and given my current ill health, I have decided to stand down from the post of chief constable with immediate effect."
On Wednesday, it was reported that Mr Hopkins was on sick leave due to a debilitating illness, after revealing he had suffered with labyrinthitis since the end of October.
He was due to retire in autumn of next year.
Mayor of Greater Manchester Andy Burnham said: "I have agreed with the chief constable, Ian Hopkins, that he will stand down with immediate effect from his duties of chief constable of Greater Manchester Police."
He said Mr Hopkins had led the force during "one of the most difficult periods in its history" dealing with budget cuts and "complex threats" such as the Manchester Arena terror attack.
He said: "In other important areas, however, the organisation has not made the progress needed. It is an important principle of policing in this country that it is operationally independent from political interference.
"I do not run Greater Manchester Police on a day to day basis. Instead, it is my job to hold the Chief Constable to account, and by extension the force for the services provided to our residents.
"At times this essential task has been made too difficult by an overly defensive culture within GMP. This needs to change if GMP is to develop the open learning culture that will allow the failures identified by HMIC to be properly addressed.
"Improvements are now overdue. So both I and the deputy mayor, whilst paying tribute today to Ian's 12 years of service to Greater Manchester Police have concluded that now is the time for new leadership, and a new era in our police force."
