Soriano delivered the message in a three-minute video sent to staff after an independent commission found City guilty of financial-rule breaches covering a nine-season period.
The Manchester City chief executive said the club's legal team would now prepare an appeal and insisted that the case against the club was built around what he described as a false central allegation.
“I want to share some information related to the ongoing disciplinary process between Manchester City and the Premier League,” Soriano said.
“A document has been made public with an opinion of the Premier League commission that is negative to our interests. I want to explain exactly what this is, the next steps and how we are going to continue to defend the club, and finally be vindicated in this process.”
Soriano argued that the Premier League's case ultimately rested on an allegation concerning the way the club's owners' money was channelled through Abu Dhabi sponsors.
“This has gone for so long that it is important to remind ourselves that the whole Premier League case against us is based on a single false accusation - that the owners' personal money was somehow and secretly put into the club via some sponsors from Abu Dhabi. This is just not true,” he said.
He pointed to evidence submitted by City during the proceedings, including financial records and witness testimony.
“Irrefutable evidence has been provided to the Premier League commission that shows that it could not happen and that it did not happen,” Soriano said.
“This includes bank statements, money transfers, witnesses and everything necessary to categorically demonstrate that the money did not come from the owner.”
Soriano also criticised the commission's conclusions, claiming that the decision disregarded evidence presented by the club.
“Surprisingly for us, and for our lawyers, after nearly two years the Premier League Commission has introduced an opinion that supports the Premier League's conspiracy theory,” he said.
“To do so, the opinion had to ignore the extensive evidence provided by the club in order to reach a conclusion that is clearly wrong.”
The club's lawyers will now appeal, with Soriano pointing to City's successful challenge at the Court of Arbitration for Sport in 2020 as a previous example of the club overturning an adverse ruling.
“Our lawyers will now file an appeal that sets out the opinion contains clear material errors of law, principle and fact and it is unsafe,” he said.
“We will now be relentless in our work. We will focus on the independent appeal process and also all other legal avenues available to us in order to win the case.”
Soriano also said City would take action to protect the club from any parties attempting to damage it, while asking employees to remain focused on their normal responsibilities.
“Very soon we will look back at this and recognise it is another time in our history when we dealt with adversity and overcame it together,” he concluded.