Iraq's main Sunni Arab bloc has said it will boycott government meetings because of legal steps being taken against one of its ministers.
Mr Hashemi denies the allegations
The Iraqi Accord Front (IAF) has six ministers, and its move is seen as a blow to the Shia-led cabinet as it tries to reconcile the two communities.
Earlier this week, an arrest warrant was issued for Culture Minister Asaad Kamal al-Hashemi, an IAF member.
The case concerns the killing of two sons of a Sunni politician in 2005.
IAF head Adnan al-Dulaimi told the BBC that the bloc's ministers would continue their work apart from the cabinet meetings.
Iraq's supreme judicial council on Monday issued the warrant for Mr Hashemi's arrest on terrorism charges.
The minister is accused of giving orders for the killing in February 2005 of the two sons of another prominent Sunni politician, Mithal al-Alusi. A bodyguard was also shot dead in the attack near Baghdad.
Iraqi government spokesman Ali al-Dabbagh said on Tuesday the warrant was a result of the "accusations and confessions" of the two men who carried out the attack on Mr Alusi.
Mr Hashemi, who is currently in Jordan, has strongly denied the allegations.
He is a member of the Iraqi Islamic Party, which stood as part of the IAF in the December 2005 election.
The party has condemned the arrest warrant as part of the "marginalising policy against prominent Sunni leaders to push them away from the political process".
It has warned the Shia-dominated government of Prime Minister Nouri al-Maliki to avoid "playing with fire by continuing the policy of fabricating lies to exclude Sunni politicians and officials from the Iraqi arena".