Hungary's Constitutional Court has struck down a law meant to shield the central bank from scrutiny over the use of public funds.

The amendments approved by lawmakers March 2 had not yet gone into effect because of a legal challenge by President Janos Ader. They were criticized by corruption watchdogs for weakening transparency and democratic checks and balances.

The Constitutional Court said in a ruling published Thursday that the amendments were unconstitutional because all funds used by the central bank were public money.

Critics' concerns have focused on some 250 billion forints ($908 million) spent by the central bank to set up foundations. Parliamentary deputies from the governing Fidesz party had argued that funds transferred by the central bank to its foundations "lose their public nature."