Begona Gomez, the wife of Spanish Prime Minister Pedro Sanchez, appeared before a judge on Friday but declined to answer questions about corruption and influence peddling accusations in a case that led her husband to consider resigning in April.

Friday's hearing in Madrid is part of a preliminary investigation into whether Gomez used her position as the premier's wife to secure sponsors for a university master's degree course that she ran.

"Our position is ... that this process is totally groundless," her lawyer and former Interior Minister Antonio Camacho told reporters after Gomez had left the tribunal.

"My client has not testified not because she has something to hide, but because her attorney recommended her to do so."

Gomez was allowed to enter and leave the courthouse through the underground parking, avoiding dozens of reporters outside.

She has not commented publicly on the case, but Sanchez has vehemently denied the accusations against her, saying they were baseless and orchestrated by right-wing political foes.

In late April, Sanchez took a five-day break from his duties to weigh whether to resign after the court opened the investigation, but ultimately decided to stay on.

The case was brought through a unique Spanish legal instrument, the "people's accusation", which allows private individuals to bring criminal complaints against third parties. Judges can choose whether or not to act, and not every accusation has led to a judicial investigation.

The complaint against Gomez was filed by Manos Limpias (Clean Hands), an anti-corruption activist group led by Miguel Bernad, a lawyer and politician who has stood as a candidate for a far-right party in European elections.

Another far-right party, Vox, also joined the plaintiff and its lawyer, European lawmaker Jorge Buxade, told reporters he will ask the investigating magistrate to call Sanchez to testify.

The investigation seeks to evaluate Gomez's conduct since Sanchez became prime minister in 2018, the court said.

Contracts related to European Union funds will be probed separately by the European Prosecutor.