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Former Barcelona President Joan Laporta defended Lionel Messi on Thursday against allegations of tax fraud that could carry a prison sentence for the Argentina star.

A Spanish state prosecutor filed a fraud complaint on Wednesday alleging Messi and his father Jorge avoided paying $5.3 million in back taxes through illegal overseas tax havens.

"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."

In the complaint, state prosecutor Raquel Amado alleges that from 2006-09 Messi "obtained significant revenue derived from the transfer to third parties of his image rights, income which should have been taxed."

Messi has denied any wrongdoing and his lawyers issued a statement on Thursday saying that he "has always punctually attended to his fiscal obligations."

Spain's Sports Minister, Jose Wert, asked for "patience" given the long legal process ahead.

"(The law) is the same for everyone," he said. "Even for the No. 1."

Laporta said 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.

The case was submitted at the court in Gava, near the Mediterranean coastal town where Messi lives. A judge at the court must accept the prosecutor's complaint before charges can be brought against Messi and his father.

If found guilty and barring an out-of-court deal with the tax office, Messi and his father could face 2-6 years in jail, according to Professor Sandalio Gomez, a sports finance analyst at the IESE Business School.

Gomez told the AP that the prosecutor's complaint appeared to be strong, while noting that hiring or establishing a company — even overseas — to manage players' image rights was legal as long as they met their tax burdens in Spain.

"(The complaint) is well argued," he said

Laporta, who was Barcelona's president from 2003-10, said he's considering a stint again in 2016 after his foray into politics. He said under his mandate, Messi directly controlled 100 percent of earnings from his image rights.

Laporta added that Barcelona did follow a common practice of paying 15% of Messi's salary to a company that controlled his image rights. He also said he didn't remember where that company was based.

"If it was a company based outside Spain, it would have been a registered company and in that sense a lawful company," Laporta said.

Messi is not the first athlete to be investigated in Spain for taxes.

Last year former Portugal star Luis Figo was forced to pay $3.26 million in income tax pertaining to image rights from 1997-99 while playing for Barcelona. In 2009, former top-ranked tennis player Arantxa Sanchez-Vicario had to pay millions in back taxes.