The councillor involved in each incident was not named by the DCC in its response, but the ODT understands 11 of the 12 complaints centre on Vandervis, who has previously been accused of such conduct by Mayor Dave Cull.
The 12th complaint, against another councillor who has not been named, was later deemed to have been without substance, the ODT understands.
Council chief executive Sue Bidrose would not be drawn on the identities of those involved yesterday, but confirmed any councillor who was the subject of a complaint was informed or cautioned their behaviour had "crossed a line".
The ODT contacted Cull and 13 of the 14 city councillors yesterday, who all said they were not involved in the complaints and had not been cautioned about any conduct.
Most had specifically checked with Bidrose or other council staff on Friday, after the information about complaints was released to them as well as to the ODT, to ensure they were not on the list.
Only Cr Vandervis failed to respond to a request for comment yesterday.
The information was released months after Cull accused Vandervis - first in emails and then publicly - of "harassment, tantamount to abuse and bullying" in his treatment of staff, particularly women.
Vandervis has ignored repeated requests for comment on the issue since then, and the DCC initially refused to release information about complaints against the councillor, citing his right to privacy.
That changed when the ODT asked for information about complaints against all councillors this term.
Councillors contacted yesterday were also reluctant to discuss the identity of anyone involved, but did not want to be tarred by the allegations either.
Rachel Elder was among those to speak out, saying a positive culture was "essential" for good decision-making and "bullying of any sort is out of order".
Aaron Hawkins agreed, describing the situation as "disappointing", while Christine Garey said such conduct was "just unacceptable".
Mike Lord questioned whether all the complaints were "legitimate", but then said the number of them seemed "quite serious".
"I suppose if there's multiple people complaining - that does give it a bit of validity, doesn't it?"
Cull said such conduct was "simply not acceptable" and could be "destructive" both to the council and its staff, whose job it was to offer "full and frank advice" to the elected arm.
"It's very important that [councillors'] power is not abused in a way that prevents them from doing their job."
The allegations of abusive behaviour by Vandervis had emerged as debate raged - initially behind closed doors - over a stalled council investigation into the merits of a unitary council, which Vandervis had championed.
He had previously been stripped of voting rights in 2015, after being found to have engaged in bullying and aggressive behaviour - including shouting and swearing at Dr Bidrose - and misleading a council subcommittee.
