MADRID, Spain -- Spain's beleaguered former King Juan Carlos came under another cloud Wednesday: a paternity suit.

The nation's Supreme Court said it will investigate a paternity claim filed against the 77-year-old monarch by a Belgian woman who says her mother had a relationship with him in the 1960s while he was crown prince.

Ingrid Sariau maintains her mother had a relationship with Juan Carlos that lasted into 1966, the year she was born. Juan Carlos and former Queen Sofia were married in 1962.

Juan Carlos could be ordered to take a paternity test if there is sufficient evidence to back the woman's case, a court spokesman said.

The spokesman said the court had dismissed a second paternity claim, saying it lacked legal basis. The official spoke on condition of anonymity because court rules prohibit him from being named.

The royal palace declined to comment, saying only that it respected the judiciary's independence.

Juan Carlos was immune from criminal prosecution and civil lawsuits while king. He lost that privilege after he abdicated in June in favour of his son, Felipe.

He said he was stepping down after a four-decade reign to allow younger blood to rally a country trying to shrug off an economic crisis and a one-in-four jobless rate.

However, the palace had become embroiled in several scandals in recent years.

Wednesday's decision comes after a Palma de Mallorca judge last week confirmed that Juan Carlos' younger daughter, Princess Cristina, would be tried on charges of tax fraud. She will be the first member of the royal family to stand trial since the monarchy was restored in 1975.

Juan Carlos was for decades held in high esteem for steering Spain from military dictatorship to democracy. He took over the throne in 1975, two days after the death of longtime dictator Gen. Francisco Franco.

But his reputation plummeted after he took a secret elephant hunting trip to Botswana in 2012 at the height of Spain's financial crisis. He later apologized for the trip.