"The Iraqiya List demands either to ensure the integrity and independence of the judiciary system in Iraq or it will withdraw completely from the Iraqi parliament and from the political process in general," al-Mutlaq said.

The multi-sectarian Iraqiya List, headed by former Shiite Iraqi Prime Minister Ayad Allawi, garnered most of the Sunni Arab vote.

Sunnis largely boycotted the 2005 elections, leading to the emergence of a Shiite-led government. The move left the once-ruling minority disaffected, which contributed to years of bloody insurgency and sectarian warfare.

The incidents follow the troubles of Iraq's fugitive Vice President Tariq al-Hashimi, who was sentenced to death in September, accused in the deaths of a lawyer and an army general.

Al-Hashimi, who is Sunni and now lives in Istanbul, denies the charges and says the accusations are politically motivated.