Iran's parliament has said President Mahmoud Ahmadinejad acted illegally by declaring himself caretaker oil minister.
The case has been referred to the judiciary, increasing pressure on Mr Ahmadinejad to quit the post.
The legislature has repeatedly clashed with Mr Ahmadinejad over key policy issues.
Today it voted to approve a report by its energy committee that found Mr Ahmadinejad's move an 'obvious violation of law', the Mehr news agency reported.
The President sacked Oil Minister Massoud Mirkazemi last month as part of a plan to merge several ministries to cut their number to 17 from 21, alarming his rivals within the conservative ruling elite.
The president has the power to remove ministers and put caretakers in place for up to three months before having to consult parliament
Mr Ahmadinejad says no one should be surprised by the reshuffle, which has been on the cards for some time.
But taking personal control of the ministry that exploits Iran's vast oil resources was seen by some as a power grab to gain tighter control over the country’s resources and a challenge to other arms of government.
'This illegal and hasty action will undermine the Islamic Republic of Iran's interests on the international level,' the conservative dominated parliament said in its report.
'Mr Ahmadinejad as oil minister has issued some orders and will continue to issue orders which are obvious examples of illegal interference in governmental financial resources.'
