Cormack, posing as an ice queen, stood on a pedestal while a body-paint artist plied her craft as part of the evening's live entertainment.
Morrison joked he would be meeting the model at the end of the evening to wash off the paint.
Cormack told the Herald on Sunday she was not happy with Morrison. "Certainly the comments made were not appreciated."
A woman at the Cuba St function said Morrison's remark was "absolutely appalling" and the model looked mortified.
Cormack, who works as a programme manager for Plunket as well as representing some of New Zealand's top sportsmen, wore a full-length strapless dress with just her arms, neck and face exposed.
Another attendee, William Hunt from Houghton Bay, also expressed his disapproval.
"It was a packed house and there was also a fashion show with young women modelling dresses, standing on podiums amongst the crowd," Hunt told Scoop.
"John Morrison ... congratulated the models and said: 'I will be meeting with one of them, in the showers, later on after the show.' My daughter was with me and she was very upset, and she was not the only one.
"This kind of 'humour' is unacceptable from anyone and especially from a candidate for the mayoralty of the capital city."
Another attendee told the WCC Watch blog: "The comment was not well received, with mostly scattered mutters. It was, I am sure, not appreciated by the poor woman."
Highly Flammable director Logan Elliott said Cormack had given her time for the charity event and one of his makeup artists had worked on her for 90 minutes.
People were able to talk to both of them as the work of wearable art was being created.
Elliot said he had been told Morrison's conversation with the model before the speech was polite and contained no references to showering together later.
Wellington Mayor Celia Wade-Brown said Morrison's comments appeared to be stuck in the 1960s along with his Basin Reserve fly-over policy. Even off-hand comments said something about a person's fundamental attitude.
Wellington lawyer and Rotarian David Howden said he did not hear the remark but had heard disturbing reports afterwards.
"If something was said that caused offence, then obviously our club is very apologetic for it."