Slamming the event as "selling women's bodies", the group is threatening to the protest the event when it takes place in Bali and Jakata in September, according to AFP.
The areas where the pagent is being held are boiling pots of radicalism, AFP reported.
It seems that the organisers of the pagent have been seduced by the conservative line the Muslims are taking, however - they have banned the bikini from the catwalk, instead preferring to make contestants cover themselves up in a sarong.
Despite the concession, it doesn't seem to have abated the anger of hardline groups such as Hizb ut-Tahrir in Indonesia, where some 90 percent of the 240 million population are Muslims, according to AFP.
"Supporting this event is the same as supporting the selling of women's bodies," said Ismail Yusanto, spokesman for Hizb ut-Tahrir Indonesia told AFP.
"Women are lowering themselves by allowing themselves to be turned into objects, to be stared at and have their bodies measured."
"They will still wear outfits that will encourage sex and immoral acts," said Chep Hernawan, the head of slam Reformist Movement [Garis] told AFP reporters.
Scientific evidence is yet to be found linking wearing a bikini with influencing your likelihood to partake in immoral acts.
What do you think of the Miss World competition? Is it inappropriate? Or should Hizb ut-Tahrir calm down?