National Party MP Dr Jonathan Coleman was allegedly punched at last week's Auckland U2 concert after it is claimed he blew cigar smoke at a woman.
Dr Coleman was at the concert as a guest of British American Tobacco.
Party leader John Key played down the incident and told the Sunday Star-Times it did not impact on his decision to confirm Dr Coleman on Friday as associate health spokesman.
Mr Key said he rated Dr Coleman highly, but if anyone had been offended by the behaviour "he would extend an apology for that".
He was not, however, apologising on Dr Coleman's behalf.
Labour Party president Mike Williams told the newspaper that if the tobacco company had invited Labour health spokespeople the invitation would have been declined.
British American Tobacco spokesman Nick Booth confirmed there was "an altercation" at its corporate box because of "a disagreement", but declined to comment further "because of the controversial nature of tobacco".
Dr Coleman told the newspaper he had no plans to lay charges and wanted to move on.