A Spanish judge has ruled that King Felipe VI's sister, Princess Cristina, and her husband must face fraud charges, opening the way to a criminal trial.

Six days after Felipe, 46, took the Spanish throne promising an "honest and transparent" monarchy, the decision on Wednesday refocused attention on a scandal that had blighted the reign of his 76-year-old father Juan Carlos.

Wrapping up a four-year pre-trial investigation, Palma de Mallorca investigative magistrate Jose Castro said Cristina, 49, was suspected of two counts of cooperation in tax fraud and one of money-laundering.

The judge said her husband - Inaki Urdangarin, 46 - is accused of embezzlement and fraud. Neither has been formally charged.

Castro has delved into allegations that Cristina's husband and a former business partner skimmed off $8m in public funds from contracts awarded to a charitable foundation, Noos.

Cristina sat on the board of Noos and Urdangarin was its chairman.Together with her husband, the princess jointly owned another company, Aizoon, which investigators suspect served as a front for laundering embezzled money.

In his 167-page ruling wrapping up four years of investigations, the judge said that in regard to Urdangarin's alleged tax crimes: "It would be difficult to have committed them without at least the knowledge and acquiescence of his wife."

Cristina's lawyers and the anti-corruption prosecutor, who argues there is insufficient evidence against her, announced immediately they would appeal the decision to pursue charges against the princess.

A palace spokesman expressed "full respect for judicial decisions" but declined further comment to AFP news agency.

A final decision on whether to put the suspects on trial is expected to be taken by the Palma de Mallorca provincial court.

If the investigating judge's findings are upheld, Cristina would be the first direct relation of the Spanish monarch in history to stand in the dock as a criminal defendant.

The scandal overshadowed the final years of the reign of Juan Carlos, who guided Spain from dictatorship to democracy after the death in 1975 of General Francisco Franco but abdicated in favour of his son on June 18.

Source: Agencies