The head of a key Philippine anti-graft agency has defied an order by President Rodrigo Duterte's office to suspend her deputy for allegedly disclosing confidential information to the media about an investigation into the tough-talking leader's alleged undeclared wealth.

Ombudsman Conchita Carpio Morales said Wednesday that the order by Duterte's office for the 90-day suspension of Deputy Ombudsman Melchor Arthur Carandang is "patently unconstitutional" and would risk the constitutionally guaranteed independence of her agency, which investigates officials for alleged corruption.

Duterte said last year he would not cooperate in an investigation being led by Carandang on alleged bank accounts he maintained when was still a city mayor but did not declare publicly as required by law. Duterte has denied the allegation and vowed to resign if it could be proven.