In unusually strong language for the mild-mannered 26-year-old, Messi told Catalan radio broadcaster RAC1 Faus knew "nothing about football" and denied demanding improved terms to the deal he signed in February that ties him to the Spanish champions until June 2018.
Faus, who oversees economic affairs at Barca, told RAC1 this month he did not understand why Messi would need a better contract given that he had only recently agreed a new one.
"Mr. Faus is a person who knows nothing about football and he wants to run Barcelona as if it were a company and it is not," Messi said from Buenos Aires, where he is continuing his recovery from a hamstring injury.
"Barcelona is one of the biggest clubs in the world and deserves to be represented by the best managers as well," he added.
"And apart from that, I remind you that neither I nor anyone in my circle has ever asked for either an increase (in salary) or a contract renewal. And he (Faus) knows that very well."
The spat between Messi and Faus is unlikely to have any lasting repercussions, particularly as the player has denied wanting more money.
Club president Sandro Rosell sought to calm the waters on Thursday, telling reporters he had not discussed the issue of an improved contract with Messi but adding that his office door was "wide open" any time Messi wanted to talk.
"I have no doubt that Messi should be the best-paid player in the world because he is the best footballer on the planet," Rosell said.
Messi's wages are the highest of any soccer player at up to $21.2 million a year, according to a list compiled by Forbes magazine in May.
He was the third-highest earner overall including sponsorship deals behind number one David Beckham and second-placed Cristiano Ronaldo.
Image: Lionel Messi
Photograph: Javier Barbancho/Reuters
Sindhu the new star as Saina endures title drought
Carnival, World Cup could hit Brazil growth in 2014
Top 10 Sporting Quotes of 2013
The Top 10 Sporting Breakthroughs in 2013
Legends Football League: Athlete rejected for not being 'lean'