Mr Davidson said overall he had been impressed by the current and former staff and elected members of the Tararua District Council.
"We have been able to work well together, often through difficult issues and, yes, we strongly disagree at times," he said. "Then we move on to the next issue and many people work above and beyond what is reasonable.
"Unfortunately, for me there are two exceptions to this - Mayor Roly Ellis and chief executive Blair King. I have been subjected to unacceptable behaviour from them, which I consider bullying and abusive.
"As councillors we represent council with outside groups, which requires information, support and actions from the mayor and chief executive at times. Their unhelpful and obstructive behaviour has, in my view, been unprofessional. This means my ability to represent the community is severely compromised and groups or projects I am associated with are at risk of being negatively impacted."
Mr Davidson told the Dannevirke News after the council meeting a longstanding issue had led to his stunning announcement.
"It hasn't been dealt with and it's been a very hard decision to come to this and resign," he said. "I could have just stayed and rode out the rest of my term, but I could not have fulfilled my role properly and I don't think that's acceptable."
Mr Davidson said he followed all the channels in an effort to resolve issues, but without success and was disappointed more than 10 years with the council had ended in such a fashion.
"I apologise to the people who elected me and have supported me through the years," he said.
It was too soon to make a decision on whether he would stand for the south ward in next year's local-body elections.
"I'm definitely having time out and now isn't the time to make a decision on my future.
"I hope they [residents] understand I am resigning today because I am being prevented from effectively representing them."
Mr Davidson said one of the most important issues he had worked hard on for constituents in Eketahuna had been water consents.
"Getting that sorted was pretty important because originally the consent was unrealistic and it took a lot of talking to get the consent we've achieved," he said.
As Mr Davidson was hugged by fellow councillors as he left the chamber, Mr Ellis thanked him for what he had done in the last four terms.