A Spanish state prosecutor filed a fraud complaint on Wednesday alleging that Messi and his father Jorge avoided paying 4 million euros (£3.4m) in back taxes through illegal overseas tax havens.
If found guilty and barring an out-of-court deal with the tax office, Messi and his father could face two to six years in jail, according to Professor Sandalio Gomez, a sports finance analyst at the IESE Business School.
"I am convinced that neither Leo nor his father have committed any infraction," Laporta told Cope radio. "The situation could be that they don't have any responsibility in these events. There can be third parties who are responsible.
"I know them and they have always wanted to act within the law, and that's how they acted with the club, at least when I was president."
Laporta said that Messi and his family lacked the financial know-how necessary to have set up the network of shell companies and tax havens in countries including Belize and Uruguay described in the prosecutor's complaint.
"They were always careful, let's say even wary, when faced with these situations that were over their heads because they didn't have the knowledge of a lawyer or a tax expert, and so they went out and got advisers," he said.