"The ruling clan seizes property, establishes control over the economy, [and] suppresses businesses and mass media," the new United Front for a Decent Future for Kyrgyzstan said.
Kyrgyzstan has been plagued by political instability since the March 2005 dismissal of long-serving leader, Askar Akayev.
Bakiyev's rule has been marked by persistent discord over the division of governmental powers.
In November, the opposition staged a week of protests that forced Bakiyev to authorise constitutional reforms curtailing his powers and giving parliament more authority.
Kulov, widely viewed as Bakiyev's strongest potential opponent, resigned as prime minister in December in protest.
Bakiyev later pushed through new amendments that gave back to him the right to form a government.