Judge Jose Castro is expected to issue the summons against Princess Cristina, 48, (whose official title is ‘la Infanta’) this week, probably on Wednesday.
If found guilty, she could face up to 6 years in prison for money laundering and another 5 for fiscal fraud, according to Spanish daily 20 Minutos.
Judge Castro is investigating the so-called Noos case in which it is alleged that Urdangarin and a former business partner embezzled €6 million ($8 million) in public funds via the Noos Institute, a charitable foundation he chaired.
Cristina was a member of the board of Noos and with her husband jointly owned another company, Aizoon. Investigators suspect that Aizoon served as a front for laundering embezzled funds.
It was reported that the money laundering charges against Cristina will claim that she accepted, managed and spent this money, in part on remodelling her palace and on the purchase of luxury goods.
The prosecution received a boost in May when tax officials provided a document proving that Urdangarin dodged €240,000 in taxes in 2007 and 2008.
National daily El Mundo reported today that Urdangarin had recently offered to pay back €337,000 to try to mitigate the case against him but that the proposal had been rejected.
Spain’s Attorney General is preparing to fight the royal summons and Cristina could yet be spared from the charges if her husband declares himself solely guilty.
Cristina has already been questioned in court this year during the prosecution of Urgdangarin.
In March she made an extraordinarily forgetful appearance in which she replied "I don't know" some 182 times during her six and a half hours in the stand, used the phrase "I don't remember" on 55 occasions, and said "I don't know anything about that" some 52 times.
The princess also replied "No" to the question "Did you know that?" on numerous occasions.
Judge Castro said at the time, “The fiscal crimes that Urdangarin is accused of could hardly have been committed without at least the knowledge and acquiescence of his wife.”
Cristina was noticeable by her absence at last week's enthronement of her brother, Felipe.