City have reportedly been found guilty of all but one of the 115 charges against the club, which could result in punishments such as a huge points deduction or even expulsion from English soccer's top division.
The club has always denied wrongdoing and Al Mubarak restated that stance in a letter to fans.
"The Premier League process still has a long way to run, and our confidence and intent in proving the club's innocence is just as strong as when this began," he wrote.
"There are so many things that I would like to be able to share with you to help you understand why we feel so confident in our position."
Confidentiality conditions, he said, prevented him from revealing that information.
"While some people have been quick to reach their own conclusions, and there is so much noise swirling around us, nothing has changed," Al Mubarak said.
"We have faced challenges together before and have prevailed. There remain many who want to undermine the momentum of our club. We will not give them that opportunity."
The Premier League accused City in February 2023 of providing misleading information about their finances over a nine-year period from 2009-18.
Questions about the Abu Dhabi-backed club's financial dealings have hung over City after supposed leaked emails and documents, likely hacked, were published starting in 2018 by German magazine Der Spiegel.
The documents allegedly showed City tried to mask the source of revenue from deals tied to Abu Dhabi, whose ruling family bought the club in 2008 and have overseen the spending of hundreds of millions of dollars on some of the world's best players over the following two decades.
In 2020, UEFA ruled City had committed "serious breaches" of Financial Fair Play regulations from 2012-16.
But a two-year ban was later overturned by the Court of Arbitration for Sport because allegations were either rejected or found to have happened too long ago to be investigated.
The Premier League's case, which accused City of more than 100 breaches including providing misleading information about its finances and failure to co-operate with the investigation, has run for more than three years.
