MADRID (Reuters) - A third ex-treasurer of Spain's ruling People's Party (PP) was charged with money laundering on Tuesday in a scandal that risks undermining Prime Minister Mariano Rajoy in his efforts to shore up the nation's economy.

High Court Examining Magistrate Pablo Ruz said in a ruling he would question Angel Sanchis on April 10 over charges he helped Luis Barcenas, another former party treasurer, to hide up to 38 million euros ($49 million) in Swiss bank accounts.

Barcenas has already been charged with using his position to take bribes and evade taxes by hiding the proceeds in Switzerland and laundering money through shell companies.

Spanish daily newspaper El Pais published papers it claimed to be ledgers kept by Barcenas from 1990 to 2009 showing the party used backhanders from companies to top up the salaries of party members, including Rajoy.

Barcenas denied the charges against him and is now suing the PP for wrongful dismissal, asking for redundancy pay.

Rajoy has also denied any wrongdoing but the case has added to Spaniards' suspicions of a deep rot now afflicting the democracy that emerged 35 years ago after the death of General Franco.

Another ex-party treasurer, Alvaro Lapuerta, was charged with involvement with the alleged backhanders earlier this month.

Spain will sink deeper into recession this year, the country's central bank said on Tuesday, still suffering from the fallout from a property bust five years ago.

($1 = 0.7763 euros)

(Reporting by Raquel Castillo lopez, Writing by Sarah Morris; Editing by Julien Toyer/Ruth Pitchford)