MANILA - Philippine President Rodrigo Duterte, whose rape jokes have sparked outrage in the past, drew fresh flak Tuesday after signing a law against sexual harassment, with campaigners saying his role as the "misogynist-in-chief" would make implementation challenging.

Duterte, who has himself been accused of sexual harassment on multiple occasions, signed the law that prohibits behavior such as catcalling and sexist slurs in April, according to the text released on Monday.

The 74-year-old was "the single most brazen violator of the law's intent with his staple macho-fascist remarks", women's rights political party Gabriela said on Twitter.

"Under this context, implementing the law will certainly be a challenge."

The law imposes fines and, in some cases, prison sentences for sexual harassment in streets, schools and offices, including wolf-whistling, groping, misogynistic slurs, as well as uninvited comments or gestures referring to a person's appearance.

Opposition Senator Risa Hontiveros, the law's author, welcomed its passage saying it would plug gaps in previous legislation against sexual harassment but added it was "only as good as how it is implemented".

Duterte has stirred controversy in the past over his treatment of women. -AFP