Spain's National Court says Prime Minister Mariano Rajoy will be called as a witness in the trial of some 40 people involved in an alleged kickbacks-for-contracts scheme that helped finance his ruling Popular Party.

The court said Tuesday that Rajoy would testify in his role as party secretary-general between 2003 and 2004, when the alleged illegal financing scheme was still operating.

It is not clear if Rajoy must testify in person or in written form. A date for his testimony has yet to be set.

On trial are former party treasurers and mid-ranking officials as well as business representatives.

Accused longtime party treasurer Luis Barcenas says there was always a scheme of illegal contributions to the party and that top officials were aware.

Rajoy and the party deny his claims.