But former Wintec chairman Gordon Chesterman, who has been involved in organising the business and community event, said this was separate.
Wintec was not paying for the event, but some of Flowers' Wintec colleagues had been invited, he said.
Chesterman said Gallagher thought it was appropriate to hold the evening event because the Gallagher Group has enjoyed a long-standing relationship with Mark Flowers.
"Sir William felt it was right and proper for the business and community sectors to get together to say farewell to Mark and thanks for doing a great job over 16 years."
The outcome of the investigations involving Flowers released in February cleared him of any major wrongdoing, despite acknowledging he should have better handled a conflict of interest with a staff member.
An Audit NZ report also heavily criticised the organisation for breaking policies and procedures in regards to overseas expenditure and could not be confident no wrongdoing had taken place.
Wintec senior adviser and director of international David Christiansen will continue as acting chief executive after the search for the new boss was put on hold while a reform of the sector was under way.
Wintec has been approached for comment.