Inaki Urdangarin, husband to Spain's Princess Cristina, as he leaves a courthouse in Palma de Mallorca, Spain. (AP Photo/Joan Llado, FILE)

Madrid - The Spanish Supreme Court has upheld a long-term prison sentence against Inaki Urdangarin, the brother-in-law of Spain's King Felipe VI, in a slightly weakened form.

The Tribunal Supremo in Madrid decided that the 50-year-old husband of Infanta Cristina would serve five years and 10 months behind bars for a number of financial crimes, a court spokesman told dpa on Tuesday, confirming media reports.

Urdangarin was convicted in February 2017 for money laundering, document falsification, fraud and the embezzlement of 6 million euros (about 7 million dollars) in taxpayers' money by a court in Palma de Mallorca.

The former handball star, who appealed against the verdict, was originally sentenced to six years and three months by the court.

In total, 17 suspects were accused in the affair, which centred on the supposedly non-profit foundation, the Noos Institute.

Cristina, who is the younger of King Felipe VI's two sisters and sixth in the line of succession, was also accused of tax evasion, before being acquitted.

She became the first close relative of a Spanish king to be put on trial in court.

Since the escalation of the financial affair more than four years ago, the Urdangarin couple have had barely any contact with the royal family, with the scandal seriously damaging the image of the Casa Real.