Barcelona have said payments made to Lionel Messi's non-profit foundation between 2010 and 2013 were above board after a claim they were made as part of his salary.

Der Spiegel, which said it had seen internal Barcelona documents, reported that tax officials found transfers worth millions of euros from the club to Messi's father Jorge and his foundation during a 2016 audit of Barca's accounts.

The report said Messi's advisers struck a deal to pay the authorities around €12 million in unpaid taxes on the payments despite maintaining they were not part of his wages.

"All of the money the club wired to Lionel Messi's foundation was for charitable purposes," a Barcelona spokesperson told ESPN FC. "The interpretations that [Der Spiegel], other media or other people can make about these donations does not change this position at all. There will be no further comment on the issue."

Lionel Messi saw his buyout clause rise from €300 million to €700 million last year. Getty

According to the Spiegel report, the club took charge of the €12m payment, which was given to Messi in the form of a loan.

The magazine said: "Messi wouldn't have to pay back the loan -- he and the club had agreed on a special premium.

"The bonus they had agreed on, to be paid in the coming season in addition to Messi's salary, was €23.1m. Of that, €9.6m was to pay back taxes on the consulting fees received by his father with €13m earmarked for the tax problems relating to his foundation.

"The net total of the bonus is roughly equal to the sum of the loan: €12m."

At the time of the audit, which Der Spiegel said was still ongoing, Messi and his father were accused of evading €4.1m in taxes by using offshore companies to hide more than €10m in marketing income from the Spanish tax authorities between 2007 and 2009.

Messi was found guilty and given a 21-month prison sentence -- although as a first-time offender he did not have to serve it. The sentence was finally replaced with a fine of €255,500 on top of the original fine of €2m.

Messi and his father, Jorge, attended court hearings in Barcelona in June relating to tax fraud. Joan Cros/NurPhoto via Getty Images

The Spiegel report also suggested that Messi, who signed a new Barcelona deal in October, would become the first footballer to pocket more than €100m annually.

It said that was made up from three contracts -- an employment contract, a contract with the company Leo Messi Management S.L., pertaining to his image rights, and one with his foundation in Barcelona.

Those agreements were confirmed by Barcelona president Josep Maria Bartomeu in September.

Der Spiegel also claimed Jorge Messi had used transfer interest from Real Madrid in 2013 to broker bigger deals for himself and his son.

Madrid, according to the report, were prepared to pay Messi's €250m buyout clause at that time.

Asked last week whether Madrid's interest had led to revised terms for the Messi family when a new deal was agreed in 2014, Barcelona vice-president Jordi Mestre said only that the club were pleased with the arrangement.

Messi could make more than €122 million in one season if Barcelona win the Treble and he is the FIFA World Player of the Year. LLUIS GENE/AFP/Getty Images

"I want to manifest that we have complete confidence in the Messi family, who we have always stood by and who we will support with everything," Mestre said. "We are more than happy with the new contract that he has signed."

Despite being agreed in June, the terms were not signed until November, with Messi's buyout clause rising from €300m to €700m.

Der Spiegel claimed that delay was due to Messi's father extracting additional money from the club, knowing they could not afford to lose his son.

According to the report, the deal will see Messi, through the three contracts, earn at least €106,347,115 per season and as much as €122,515,205 if Barca win a Treble and he is crowned FIFA World Player of the Year in the same year.

Asked about the revelations, the club spokesperson said Barcelona "never comments on contracts signed with players and never will."