Crude exports in February averaged 2.596 million barrels a day -- almost a million barrels less than planned.
The exports grossed about USD 3.402 billion, based on an average price of USD 46.795 per barrel, said the ministry's spokesman, Assem Jihad.
January's daily exports averaged 2.535 million barrels, bringing that month's revenues to USD 3.258 billion.
Iraq's 2015 budget is based on an expected price of USD56 per barrel with a daily export capacity of 3.3 million. The nearly 119.6 trillion Iraqi dinars budget (about USD102.5 billion) runs with a deficit of 25 trillion dinars (about USD21.4 billion).
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Government forces, Iraqi Kurdish fighters and Shiite militias have since managed to claw back some of the territory from the IS, with the help of US-led coalition airstrikes.
The militants control a number of oil fields and have shut down facilities in nearby areas.
Also, a major export pipeline that traverses restive Sunni-dominated areas of northern Iraq was shut down earlier last year due to attacks, preventing Iraq from exporting around 400,000 barrels a day.
The heart of Iraq's oil industry, which is in the mainly Shiite south of the country, has been spared the militants onslaught.
But its export facilities on the Persian Gulf are often affected by bad weather, causing a dip in exports.
Jihad, blamed bouts of bad weather for the low exports in February.
Iraq has the world's fourth largest oil reserves, some 143.1 billion barrels, and oil revenues make up nearly 95 per cent of its budget. The price of oil has fallen by about half since June to less than USD 50 per barrel.