Iraqi Communications Minister Mohammed Tawfiq Allawi told AFP he quit his post on Monday, accusing Prime Minister Nuri al-Maliki of "political interference" in his ministry.
Allawi's resignation is the first by a cabinet minister since Iraq's national unity government was formed in December 2010, and comes just months after opponents of Maliki attempted to oust him via a no-confidence motion.
"I resigned because Maliki refused to... (stop) political interference in my ministry," Allawi said by telephone from London, referring to demands he made in late July for an end to meddling in his ministry.
He specifically pointed to attempts to control who could appoint and transfer senior officials, alleging that the prime minister asked that a number of director-generals in the communications ministry be transferred to different ministries against Allawi's wishes.
"Some of our DGs who are very truthful, they are working very hard, he (Maliki) asked me to transfer them back to their previous ministries," Allawi said. "I asked to keep them but he refused."
Communications Ministry spokesman Samir al-Hasoon said that the ministry had received official documentation confirming Allawi's resignation.
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Allawi is a member of the mostly Sunni-backed Iraqiya bloc that attempted earlier this year to withdraw confidence from Maliki's government.
"I required certain conditions from the prime minister, to stop the political interference in my ministry," Allawi told AFP. "Otherwise, I told him I am not ready to work at the ministry with this big interference."
"I told him, either you fulfil those conditions or accept my resignation. He decided after one month to accept my resignation."
Allawi said he made the demands to Maliki on July 28.
Allawi's resignation is the latest bout in a protracted political row between Maliki and his opponents, who have accused him of monopolising power and exhibiting dictatorial tendencies.
Maliki, for his part, insists he is being restricted by an unwieldy coalition government.
The dispute erupted in December when Iraqiya staged a parliamentary boycott and authorities issued an arrest warrant for Vice President Tareq al-Hashemi, a senior Iraqiya leader, on charges he ran death squads. Hashemi has persistently dismissed the accusations as politically-motivated.
The communications ministry under Allawi had been planning several large projects that remain unfinished, including the potential issuing of a license for a fourth mobile phone operator, and the allocation of 3G spectrum to boost mobile data speeds in Iraq, where users still rely on slower 2G transfers.