Iraqi Oil Minister Hussein al-Shahristani is expected to be summoned before parliament soon to face a grilling for failing to boost crude exports from the oil-rich nation, MPs said on Tuesday.

Lawmakers have gathered 140 signatures, more than enough for Shahristani to be called before the assembly to answer questions about the ministry he has headed for the last three years.

If MPs are dissatisfied with the minister's explanations, a no-confidence motion could follow -- and he could potentially be fired by Prime Minister Nuri al-Maliki.

"The reason is that he has performed badly and parliament wants to ask questions and hear what the minister has to say," Mahmoud Othman, a Kurdish MP, told AFP.

"There could be a motion of no-confidence and this demand will be presented to the premier who will take a decision on what to do."

Ezzedine Al-Dawlah, a Sunni Arab MP in the largest Sunni bloc the National Concord Front, confirmed the plans but could not say when Shahristani would go before lawmakers.

The summons comes at an especially sensitive time. Iraqi Trade Minister Abdel Falah al-Sudani stepped down on May 14 amid allegations of corruption and embezzlement linked to the nation's food assistance programme.

His resignation was accepted by Maliki on Monday after lawmakers began to prepare a no-confidence motion.

Allegations of graft have also surrounded Shahristani although oil ministry spokesman Assem Jihad insisted that parliament was only interested in understanding oil production.

"The summons is not related to corruption, but to examine production rates." Jihad told AFP.

"We hope that the questions will focus on professional matters and not politics or the settling of old scores," he added.

During his tenure, Shahristani has failed to increase production above 2.2 million barrels per day and taken only tentative steps toward drumming up foreign investment.

Iraq has said it aims to pump six million barrels per day within the next four to five years as new projects come online. It has the world's third largest proven reserves of oil, with more than 115 billion barrels, behind only Saudi Arabia and Iran.

The Kurdish autonomous region has ramped up pressure on Baghdad to be allowed to export their oil and gas in their bid to better control their own energy resources, intensifying a feud over oil-sharing revenues.