The Spanish judge investigating a kickbacks-for-contracts scandal ruled Monday that former Sen. Luis Barcenas, who was found to have roughly 22 million euros (roughly $30 million) in Swiss bank accounts, must surrender his passport.

In his ruling, Judge Pablo Ruz also ordered Barcenas to appear every two weeks before the National Court.

The ex-lawmaker and erstwhile treasurer of Spain's governing Popular Party testified Monday in Ruz's courtroom.

Barcenas said he managed to accumulate as much as 30 million euros ($39 million) in Switzerland, thanks above all to his stock market investments, but that later the amount dropped to 22 million euros ($30 million) when his partners, whom he refused to identify, began withdrawing money.

Attempting to explain his fortune, Barcenas also denied any links between his Swiss accounts and the finances of the conservative PP.

The discovery of the Swiss bank accounts and an ostensible secret PP ledger attributed to Barcenas were subsequently reported in the media.

The purported ledger is said to include the payment of undeclared cash to top party leaders, including current Prime Minister Mariano Rajoy, who denies any wrongdoing.