If the party participates in the September elections, it will be giving the government a "stamp of approval," Khalil Marzooq, a leader of the party, told a group at a rally near Bahrain’s capital.
The group disagrees with how the government treated protesters earlier this year, Marzooq said.
Bahrain was one of several Middle Eastern and North African countries embroiled in anti-government protests earlier this year.
Protesters took to the streets of Manama to demand reform and a constitutional monarchy, and later called for the removal of the royal family.
The ruling royal family — Sunnis in a majority-Shiite nation — accused them of being motivated by sectarian differences and supported by Iran.
A government crackdown quelled the protests.
