Prosecutors said they have until the end of June to decide whether to charge the Real Madrid star, based on evidence from an investigation by tax officials, who believe the Portuguese may have committed wrongdoing.

Ronaldo attempted to regularise his tax situation in Spain in 2014 by paying an extra €5.6m, but the tax office believes Ronaldo should have had to pay a further €15m.

The tax office asked prosecutors to press charges against Ronaldo for tax fraud and requested a minimum five-year jail term.

Prosecutors said that if they decided to charge the Portugal captain, and if he was subsequently found guilty by a court, he would face a prison sentence of at least 15 months -- one quarter of the five years.

At that level of sentence, it would be unlikely Ronaldo would go to jail as a first-time offender.

The union of employees (GESTHA) at Spain's tax office "lamented" the delay in referring the case to prosecutors but welcomed the move by the tax authorities.

In December, news outlets including El Mundo received "Football Leaks" documents that claimed that Ronaldo, among other players and coaches, had avoided tax on earnings from image rights by having large sums in offshore companies in the British Virgin Islands, a tax haven.

Ronaldo's agents vehemently denied the claims and said the 32-year-old is "fully compliant with his tax obligations."

The allegations come one day after Spain's supreme court upheld Lionel Messi's 21-month suspended sentence for his conviction of tax fraud last year.