Lionel Messi is optimistic his advisers will be able to sort out his tax problems after he and his father were accused of defrauding the Spanish authorities last month.

The Argentine World Player of the Year and his father Jorge, who both denied wrongdoing, allegedly hid more than 4 million euros ($5.3 million) by filing false tax returns for the years 2006 to 2009.

The prosecutor's office for tax crimes in Catalonia said the sale of Messi's image rights had been hidden via a complex web of shell companies in Uruguay, Belize, Switzerland and the United Kingdom.

"I am very calm," Rosario-born Messi, who has been resident in Barcelona since 2000 and gained Spanish citizenship in 2005, told a post-training news conference on Wednesday, his first since returning from holiday.

"I never take care of that stuff myself and neither does my father," the 26-year-old added.

"We have our lawyers and our wealth managers to take care of that and we trust them and they will sort this out.

"The truth is that I don't have a clue about all this and that is why we have people taking care of it."

Messi is one of the world's highest-paid athletes and earns just over $20 million a season in wages and bonuses, according to Forbes magazine.

He also pulls in about $21 million in endorsements from sponsors including Adidas, PepsiCo and P&G and is 10th on Forbes' latest list of top-earning athletes.