Hull Council leader Steve Brady said he found out through the Media on Friday night about the chief executive of Welcome to Yorkshire's departure, which followed an internal investigation into concerns over his behaviour towards staff and his expenses payments.
Councillor Brady attended his first meeting earlier this month, but said nothing "untoward" was reported at the meeting.
He said he was sure "full explanations" would be given.
He said: "It was the first I knew, it will have come as a shock to most people.
"I am sure full explanations will be given.
"It is always in the best interests of any organisation to be open and transparent and I am sure that will happen in this case."
Welcome to Yorkshire was responsible for organising the Tour de France's 2014 Grand Depart in Yorkshire and its subsequent legacy race, the Tour de Yorkshire.
In a statement on Friday night the tourism body confirmed that Sir Gary's resignation on health grounds follows “errors of judgment regarding his expenses at a very difficult time for him and his family”.
The amount involved has not been disclosed but it is understood it is a five figure sum.
A spokeswoman for the organisation confirmed Sir Gary has agreed to “voluntarily reimburse” Welcome to Yorkshire for all the money which is owed.
Sir Gary, 54, issued an apology following his resignation, and asked for “time and space to heal” as he maintained that his health is now his “main priority”.
He said: “Over the last 10-and-a-half years, I have always tried to set the highest standards of personal performance and leadership. Where this has been achieved, I am grateful and when, on occasions, I have fallen short, I apologise. My health is now my main priority. I ask for time and space to heal.”