His report identified a number of key issues that led to the loss of accreditation, but in mitigation also noted the pressures on the organisation and the chief executive as a direct result of the disastrous series of earthquakes that hit the city beginning in September 2010.
The report was of the view that in normal times a chief executive would have been expected to be aware of the issues relating to accreditation, but found that Mr Marryatt was not aware of this situation until shortly before he informed the council.
The report stated that the chief executive "has been very focused on pursuing specific council objectives, including the signature projects and cost sharing agreement with Government. Christchurch City Council is not in a business as usual situation".
Mr Marryatt accepts that, despite the presence of mitigating factors, the final responsibility for the loss of accreditation must rest with him as the council's chief executive, a council release says.
"Taking this into account, and with local government elections due in October, Mr Marryatt feels this would be a suitable time to resign," it states.
"The parties see this as enabling the new council to appoint a new chief executive to work with them in continuing the rebuild of Christchurch."
It has been agreed that Mr Marryatt's last day of employment will be November 30, and he will be on full pay till then.
He will then be paid $269,264.00 gross which consists of his notice period of three months paid in lieu, and a severance payment equal to three months' remuneration.
"It has been agreed that between now and November 30, Mr Marryatt will not be required to perform the chief executive role but rather he will be available as required to assist with handover matters and in the transition to a new council and chief executive," the council statement says.
"Mr Marryatt wishes to thank council staff for their ongoing support, work ethic and focus on making a difference during extremely stressful and trying times.
"There will be no further comment from the mayor, Mr Marryatt or the council on this matter.''
The McGredy, Winder & Co report will be made available on the Christchurch City Council website by 6pm today.