Duterte, 71, said he wanted to be referred to simply as "President" in all official communications in a statement from his office.
The first president from the vast southern region of Mindanao, Duterte has reinforced his image as a maverick outsider focused on a brutal anti-crime war instead of the opulence of the presidential palace.
"In keeping with his populist presidential style, he encourages less 'ceremonial' communications," Duterte's spokesman Ernie Abella told AFP.
In a nation where bosses are addressed as "ma'am" and "sir", Duterte ordered that his cabinet members be called "Secretary" instead of "Honourable", as previously was practice.
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Since assuming the presidency on June 30, Duterte has repeatedly shunned tradition and chose to take his oath of office in the presidential palace instead of at a mass gathering in a national park to avoid causing heavy traffic in the gridlocked capital.
Even presidential fashion has changed, with Duterte wearing jeans at military parades and seen rolling up the sleeves of the traditional "barong" shirt worn for formal occasions.
In his first address to congress on next Monday, Duterte has ordered guests to wear business attire doing away with the long-running custom of lawmakers parading on the red carpet in ostentatious long gowns and suits.
"We will downplay the event. It will not be a fashion show," a spokeswoman said
