A Spanish judge has recommended that six people accused of running a slush fund for the ruling conservative Popular Party stand trial for tax fraud.

Investigating Judge Pablo Ruz says he has evidence showing that from 1990 to 2008 the suspects, including two former party treasurers, operated a system for party donations by companies that were not declared to authorities.

The judge ruled Monday there was no evidence of illegal party financing but that money was used to renovate the party's headquarters.

The case follows media publication of ledgers outlining the scheme kept by former party treasurer Luis Barcenas, who claimed Prime Minister Mariano Rajoy knew about payoffs.

Rajoy has denied the accusation and is not among the six.

Ruz will hear other legal recommendations before making a final decision.