There is no basis for a graft probe into the business affairs of Spanish Prime Minister Pedro Sanchez's wife Begona Gomez, government spokeswoman Pilar Alegria said Tuesday.

"We know that there is absolutely nothing here," Alegria told reporters after a court issued a summons for Gomez to appear as part of a preliminary probe into her business ties, saying the case is based on "lies and disinformation".

"What we have here is a mudslinging campaign by the right and the far-right, the Popular Party and Vox," she told reporters following the weekly cabinet meeting.

The court opened the probe into Gomez for suspected influence peddling and corruption on April 16 following a complaint filed by an anti-graft NGO linked to the far right.

The group, Manos Limpias (Clean Hands) says its complaint is based on media reports. It has previously filed a litany of unsuccessful lawsuits against politicians in the past.

The case is mainly focused on public contracts awarded to a businessman who had professional ties with Gomez.