"The Messi family wants to make clear that Lionel Messi has not carried out any of the acts attributed to him, and accusations he created a...tax evasion plot, including a network of money-laundering, are false and insulting," it said in a statement.
The scandal erupted on Sunday when media groups made public a year-long worldwide investigation into a trove of 11.5 million documents leaked from a Panama-based law firm that exposed a tangle of offshore financial dealings by the elite.
Among the accused are close associates of Russian President Vladimir Putin, relatives of Chinese leader Xi Jinping, Iceland's Prime Minister Sigmundur David Gunnlaugsson as well as sports celebrities and screen stars.
Messi and his father are named as owners of a Panama company that had not previously been disclosed during a Spanish probe into their tax affairs.
"The Panama company to which they refer to is a totally inactive company that never had any funds or any open current accounts," the Messi family said.
They added that the firm was created by the family's former tax advisers and that everything had since been brought into line where Messi's fiscal situation was concerned.
Barcelona published a message of support to their star player on their official website.
"The club supports the arguments which the Messi family published in a statement today," said the Barca statement.
"Since the very first moment that the 'Panama papers' which accuse Leo Messi were released, FC Barcelona has sent its affection and support to the player and to his whole family.
"The Club makes all of its judicial means, fiscal and administrative, at the family's disposal in order to make his actions and honour clear in this case."
Messi and his father Jorge have been charged with tax fraud in a separate case for allegedly failing to declare €4.16 million ($4.74 million) in taxes related to his image rights between 2007 and 2009 through front companies in Belize and Uruguay.
The pair are accused of ceding the player's image rights to the companies in order to avoid declaring money made from lucrative deals with sponsors in Spain.
Their trial in this case is set to begin on May 31st at a court in Barcelona and is expected to run until June 3.
Lawyers acting on behalf of the tax office have asked for both defendants to be slapped with prison sentences of 22-and-a-half months.
Both father and son have denied the accusations and instead blamed a former financial advisor.
Jorge Messi made a voluntary corrective payment of four million euros in August 2013 which is expected to mitigate any sentence.
Even if convicted it is unlikely that either Messi or his father would enter prison as jail terms of less than two years are usually suspended for first-time offences in Spain.
In December Messi and his father were cleared of separate allegations relating to charitable friendlies played in 2012 and 2013 after a judge heard testimony from an Argentine businessman who organised the matches.
The player had been investigated in that case to see if he had failed to declare to the tax man any revenue made from taking part in a series of friendlies in Mexico, Colombia, the United States and Peru.