The mayor who guided Christchurch through a series of devastating earthquakes, Bob Parker, has announced that he will not seek re-election.

Parker told Campbell Live tonight he will not contest the Christchurch race in October.

"I just don't think I have another three years ... left in me."

"It feels to me like a pretty dirty election... there's a lot of people trying to score a lot of hits. I think the city does actually deserve a fresh start."

Mayoral hopeful Lianne Dalziel said she felt "incredibly sad" after hearing Parker's announcement.

"He has given so much to the city."

She was not ruling out the possibility of another mayoral candidate coming forward to join her in the race.

Prime Minister John Key issued a brief statement following Parker's announcement.

"Bob's dedication to his city could never been questioned, and he's served admirably in circumstances that would have been too much for many people," he said.

Deputy mayor Ngaire Button said "as strange as it is to say, I'm shocked but I'm not surprised".

"He's worked and worked and worked, and served and served and served, and he's had little encouragement along the way. It's been a tough three years, it's been endless criticism and endless embattlement."

Despite announcing his intentions to stand for his third term earlier this year, Button said: "I don't think Bob's been 100 per cent certain all the way through that he wants to do another term".

She hoped the city would now "pause and show him some respect".

Parker's decision follows Wednesday's announcement that council CEO Tony Marryatt had gone on indefinite leave.

Marryatt was on leave while investigations were underway to work out why action had not been taken to address the council's issues with building consents.

Issues with the council's consenting process led to a Crown manager being appointed to the unit yesterday.

Parker told Campbell Live he had a lot of respect for Marryatt.

Marryatt was not perfect but he had worked hard, he said.

"All I see that gets directed at him is a lot of negativity."

Parker said the decision to quit was quite emotional.

"I have to think of my own well-being, and those closest to me, and I don't believe I have the energy to lead this city for another term."

Parker later released a statement saying he was tired.

"I feel exhausted having worked non-stop over the past six years in office and I know that I can't sustain the pressure and stress of this job for another three."

Parker said he had put his "heart and soul" into his job.

"It's been one heck of a three years.

"It's taken a great deal of self-examination to walk away from this job. Everyone deserves a fresh start and this city needs to be led by someone who has the energy and drive to take them on this journey."

Parker said there was still time for someone else to put their hand up for the job.

"There is a responsibility that rests with the chair of an organisation and I have to face up to that responsibility."

It appears many councillors were not advised of Parker's plans to pull out of the race.

Councillor Tim Carter said tonight he had not known of the mayor's plans to appear on the TV show.

"I'm not surprised that councillors weren't told. That's not how he's operated this term. Bob and Marryatt were very close, and Marryatt leaving would have had a large bearing... and the disruptive events of the last week or two have had a huge effect on both Bob and Tony," he told Fairfax Media.

"I would like to acknowledge that he did a very good job immediately after the earthquakes, but Christchurch requires a different set of skills than he possesses going forward."

When Fairfax Media visited Parker at home tonight, a council spokeswoman said the mayor would not be making further comment tonight.