The Iraqi National Accord (INA) party on Tuesday lodged a formal complaint against the front-running Shia coalition, the Unified Iraqi Alliance (UIA), for violating state law by playing the religion card in its campaign.
INA political chief Imad Shibib called for a ban on UIA pamphlets and posters telling voters that Shia spiritual leader, Grand Ayat Allah Ali al-Sistani wanted them to vote for the 228-UIA candidate list.
Shibib also said policemen linked to former Shia militia, the Badr Organisation, were intimidating voters by handing out the UIA's pamphlets in the southern city of Basra.
Hadi al-Amri, head of the Badr Organisation, denied the allegations and defended the UIA's use of al-Sistani in their advertising.
Most Shia look up to al-Sistani for
advice and guidance
But Iraq's Independent Electoral Commission, which is administering the vote, acknowledged that parties were violating the law through their religious-flavoured advertising.
"The IEC has received many complaints from political entities - over some lists using religious symbols and fatwas in their electoral campaign which goes against the rules signed by the entities," the Electoral Commission said in a statement.
"The IEC is studying these complaints," it added.
In November, IEC chairman Abdul Hendawi said all religious emblems were banned from the electoral race.
The UIA, comprising the two largest Shia political parties - Dawa and the Supreme Council for the Islamic Revolution in Iraq - has plastered cities with posters featuring the image of al-Sistani.
Hundreds of thousands of Shia look to al-Sistani for guidance and advice.
But Shibib and the INA have contested al-Sistani's backing of the UIA list and demanded his name no longer be attached to political advertisements.
"If you use al-Sistani's name or picture, this is against the election law. It is not allowed. It is not correct to campaign based on the religious names," Shibib said.