The former minister was the MC at the Esri Users Conference dinner at SkyCity last Tuesday.
A guest told One News that Mr Williamson was making jokes which "made many feel uncomfortable".
Another told One News that Mr Williamson, who was MC for the gala dinner, was acting "like it was a stag do".
The event's organisers, Eagle Technology, issued an apology which said any offensive comments did not reflect its beliefs and values.
One News reported that Mr Williamson said he regretted any offence caused in the statement, and said his intention was not to offend but entertain.
Matt Lythe, GIS sales manager at Eagle Technology, told the New Zealand Herald tonight that it was a private matter and the company would not be commenting on it at all.
Under the heading "Please accept our apology", event organisers Eagle Technology sent an email to guests to say sorry for Mr Williamson's actions.
"Corallie Eagle, Duane Eagle and all of the Eagle Technology staff offer our sincere apologies to all who attended the NZEUC Conference Gala Dinner last Tuesday night, for the content and references made by the MC, Maurice Williamson."
It went on to say that Mr Williamson had asked the company to convey his apologies also.
"His intention was certainly not to offend, but rather to entertain and he regrets the offence caused."
The email said Eagle Technology and the dinner organisers were not aware of the content "that was to unfold", and assured guests that any offensive comments or content did not reflect the beliefs and values of the organisation.
Mr Williamson has been the MP for Pakuranga since 1987.
He is also a former Minister of Research, Science and Technology, Communications, Statistics, Information Technology, Transport, Local Government and Broadcasting.
Mr Williamson resigned as a minister last May following revelations he contacted a top-ranking police officer after businessman Donghau Liu was arrested on domestic violence charges.
He also made international headlines and became an icon for his "big gay rainbow" speech at the final reading of the same-sex marriage bill.
