In a thinly veiled attack on president Sepp Blatter's leadership, Michael Garcia reiterated the need for "greater transparency".
"The investigation and adjudication process operates in most parts unseen and unheard," continued Garcia.
He added that the organisation needs a "leadership that sends a message that the rules apply to everyone".
Talking about the current investigation process, Garcia said: "That's a kind of system which might be appropriate for an intelligence agency but not for an ethics compliance process in an international sports institution that serves the public and is the subject of intense public scrutiny."
American lawyer Garcia concluded his lengthy investigation into the 2018 and 2022 World Cup bidding process last month and handed his report to Fifa's ethics adjudicator Hans Joachim Eckert, but he is disappointed by the world governing body's insistence on keeping his report confidential.
In a keynote speech at an event organised by the American Bar Association in London, Garcia added: "The natural next step of the development of an effective ethics process at Fifa is greater transparency.
"The second element that is vital to fulfilling the promise of this reform process is tone at the top.
"More simply put, the second element an institution like Fifa needs in order to meet the challenge of ethics enforcement is leadership. An ethics committee - even a serious, independent ethics committee backed by a strong code of ethics - is not a silver bullet.
"What is required is leadership that sends a message that the rules apply to everyone; leadership that wants to understand and learn from any mistakes or mis-steps the ethics committee may have identified; leadership that makes it clear to everyone - this is what we've set up the ethics committee to do, this is why they do it, and this is what they've done.
"It's that kind of leadership that breathes the life into a code of ethics. Because true reform doesn't come from rules or creating new committee structures. It comes from changing the culture of the organisation."
Garcia's views on publishing the report have been supported by a number of Fifa executives, including Uefa president Michel Platini and Britain's representative Jim Boyce.
But Fifa president Blatter insists the contents of the report must remain confidential, and that no member of his executive committee made a specific request when the issue was raised in a meeting earlier this month.
Garcia said other sports organisations have already demonstrated the value of transparency, highlighting the publication of a report into allegations concerning the 2002 Winter Olympics being awarded to Salt Lake City, which allowed the International Olympic Committee to "move forward".
He added: "We have seen that recently with the NFL where a lack of transparency in its initial investigation concerning Ray Rice fostered scepticism and questions about the integrity of its leadership. Now the NFL has has to bring in outside counsel to investigate the investigation.
"Notably, the NFL has made clear the results of the new investigation will indeed be made public.
"That in turn would help foster a culture of compliance internally and would promote more confidence in the system from the public, its partners and the millions of fans who follow and love the game."
Garcia said the aim of transparency is not "to embarrass certain individuals" or "harm the organization", but rather the opposite.
"It's one thing to tell people that a rigorous process is in place. It's another thing to show them how that process works and what it has uncovered," he explained.
"Fifa built the system that should inspire confidence that things have changed for the better. Showing that to the public serves Fifa's best interest."

7 June 2016 Last updated at 19:29 BST
Firefighters pumped water out of several properties in Penicuik and the council said work was ongoing to clear water at Mauricewood Primary School in the town.
The Met Office has issued a yellow 'be aware' weather warning covering a band up the middle of Scotland from the Borders to the Highlands.
Fifa's chief independent ethics investigator has called for a "change of culture" at the organisation.
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Heavy rain has caused travel problems, flooding a number of routes in the Scottish Borders.