Dermot Desmond has hit out at "contemptible" suggestions that he is not a true Celtic fan as he insisted his shares were not for sale.
The club's principal shareholder has come under fire from some supporters after Celtic failed in their quest for a record 10th consecutive title.
The Irishman took exception to recent comments in the media from former Celtic director Brian Dempsey, who was a key player in the push to topple the dynastic regime that controlled the club until 1994, when Fergus McCann assumed control. Desmond first put money into the club at the same time.
Dempsey called for fans to raise money to buy out Desmond, claiming he had lost interest and commitment and never had passion for Celtic.
In an interview published on Celtic’s website, Desmond said: "This is a contemptible suggestion. I am as passionate about Celtic as any other supporter. My shares are not for sale.
"When I think about the strength of this club today and the playing success that we have enjoyed to date, these are entirely attributable to being financially strong and being professionally managed under stable ownership.
"When I look back at the record of the club since 2001, we have achieved remarkable success and encountered only a few set-backs along the way.
"This season has been one of them, but it does not re-create the conditions of the early 1990s, as Mr Dempsey would like to have us believe."
"In a professional manner we conduct our business behind closed doors, we don't seek public acclaim for everything we do. Critics are in no position to judge what they cannot see."
Desmond also strongly defended the Celtic board and its composition.
"One of Fergus McCann’s tenets was that the club would be run professionally and that we should never return to the position he inherited where the entire existence of Celtic could be jeopardised by mis-management and unacceptable levels of indebtedness," he said.
"Celtic is and will continue to be run on a meritocratic basis by the best executives available at the time.
"There is no member of the Celtic board that I personally knew before they were appointed. We have maintained this policy and it has endured the test of time.
"In a professional manner we conduct our business behind closed doors, we don’t seek public acclaim for everything we do. Critics are in no position to judge what they cannot see.
"We are very fortunate to have Ian Bankier as our chairman and he leads a diverse and extremely talented board.
"We could not have had a better CEO, nor a more committed Celtic supporter than Peter Lawwell. He has built a solid platform upon which our new CEO, Dominic McKay, can build.
"With every board appointment we make, we undertake a thorough recruitment process of researching, investigating, interviewing and negotiating, unknown to all except the Celtic board members.
"That will be the same process that is being implemented in recruiting our next manager."
Desmond said that both Lawwell and McKay would be involved in the hunt for a successor to Neil Lennon, who left Parkhead in February after a tumultuous campaign which saw Celtic lose the title to Rangers, suffer major disappointment in Europe and lose at home to Ross County in the Betfred Cup.
But Desmond dismissed claims that anyone could have foreseen their struggles after nine consecutive titles and 12 domestic trophies in a row.
"Firstly, the season is not over yet, as we are still in the Scottish Cup," he said. "However, my current thoughts are that this season has been extremely disappointing.
"Decision-making in football is not an exact science and I accept without qualification that we have made some wrong calls. We will endeavour to learn from those.
"However, the conjecture coming from some journalists, commentators and pundits that they foresaw the outcome of this season is entirely disingenuous in my opinion.
"Regardless of whether we won the league or not this year, we knew that the 2021/22 season would be a transitional year for the team.
"A number of the existing squad would more than likely be departing or returning to their parent clubs, but we felt that, in order to give the team the best chance of success this year to achieve the overriding ambition, we should endeavour to retain these players, despite receiving a number of substantial bids.
"In so doing, we recognised that this would add to the recruitment requirements for the subsequent season.
"We recognise that we have under-performed both on and off the pitch and must do better."