Spain's Princess Cristina has lost a legal battle to avoid being tried for tax fraud and is expected to give evidence next month in a corruption trial also featuring her husband and 16 other defendants, a panel of judges ruled.

Lawyers for the sister of King Felipe VI, a prosecutor and a state attorney representing Spanish tax authorities earlier this month all said the charges against Cristina should be thrown out because government officials agreed she had committed no crimes and should face at most an administrative fine for tax evasion.

But the judges disagreed, according to a statement released by the court.

That means 50-year-old Cristina will face two counts of tax fraud carrying a maximum prison sentence of eight years for allegedly failing to declare taxes on personal expenses paid by a property company she owned with her husband, Inaki Urdangarin, an Olympic handball medallist-turned-businessman.

The judges ended up siding with an investigative judge who spent four years probing the case and ruled she could be tried because of evidence presented by private anti-corruption group Manos Limpias (Clean Hands).

During the trial, the judges will have to weigh whether the couple criminally abused the Aizoon property consulting firm described in court documents as a "front company" to fund luxury holidays, throw parties at their modernist Barcelona mansion and pay for salsa dancing classes.

The trial is the first time that a member of Spain's royal family has faced criminal charges since the monarchy was restored in 1975.

Urdangarin and others face charges of embezzling up to 6.2 million euro (£4.7 million) from contracts that were allegedly inflated or never honoured. The princess' husband, formerly the Duke of Palma, is accused of using his title to land the deals for the Noos Institute he ran with business partner Diego Torres.

The case is being heard in Palma de Mallorca, the regional capital of Spain's Balearic Islands, because many of Urdangarin's business deals under investigation were for the islands.

Cristina denied knowledge of her husband's activities during a 2014 closed-door court appearance, but the investigative judge decided she could be tried for tax fraud allegedly committed in 2007 and 2008.

Details about the couple's regal lifestyle that emerged from the pre-trial investigation from 2011-2014 outraged Spaniards as the country teetered on the edge of an economic crisis and the unemployment rate hit 27%.

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The Royal Palace said it had no comment to make beyond reiterating its total respect for the judicial decisions.

The trial is due to resume on February 9 with the accused beginning to give evidence.

Cristina is scheduled to be the last to give evidence and is expected to do so by February 26.