The first minister to quit Iraqi premier Nuri al-Maliki's unity government criticised the prime minister for turning a blind eye to worsening corruption among his loyalists, in an interview with AFP.

Former communications minister Mohammed Tawfiq Allawi, who resigned on August 27, added he was holding documents pointing to graft within the government, but declined to give details, insisting instead they would be released at an unspecified future date.

He said he was "100 percent sure that the people surrounding al-Maliki, they are corrupt people, very close to him, they are highly corrupt people."

"But definitely, he knows the corrupt people, but those who are loyal to him, he never takes any action. He allows them to be more corrupt, and it is very obvious," Allawi said at his west London home.

The ex-minister is a Shiite Muslim member of the secular Sunni-backed Iraqiya bloc that is part of Maliki's unity government, but has long been at odds with the premier.

He is also a relative of former prime minister Iyad Allawi, one of Maliki's main rivals.

He said he had told Maliki directly, "those people who are loyal to you, they are corrupt people, and you never take any action against them."

The ex-minister said the level of corruption in Iraq was "huge", and that rates of commission on contracts were sometimes as high as 70 percent, but declined to point to specific instances of corruption, or which ministries had particularly high rates of graft.

"You know Iraq is at the top of the list of corrupt countries, at the level of Somalia, Myanmar," Allawi said, adding: "Those countries, they have no revenue, their budget is... millions of US dollars, while (Iraq's budget) is for the last year $100 billion."

"The real corruption is in Iraq, not in these countries."

Iraq regularly ranks atop global rankings of the most corrupt countries in the world.

Most recently it was the ninth worst country in Transparency International's Corruption Perceptions Index, and diplomats and potential investors often point to graft as an impediment to doing business there.

Allawi said that corruption in Iraq was, if anything, getting worse, telling AFP: "The level of corruption, really it is much more worse than the previous days. It is increasing year after year."

The former minister stepped down last month, accusing Maliki of "political interference", in particular complaining of attempts to control who could appoint and transfer senior officials.

His resignation was the latest bout in a protracted and wide-ranging 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.

Allawi's remarks on graft were part of a wide-ranging criticism of Maliki's record as prime minister, arguing that the premier had accomplished nothing since Iraq's national unity government was formed in December 2010 following nine months of post-election stalemate.

Parliamentary elections are next due in 2014.

Allawi pointed to still-poor electricity provision nationwide, and a lack of improvements in daily life for ordinary Iraqis, particularly in Baghdad, as well as continuing deadly violence across the country.

"The only thing which he has achieved is deepening sectarianism," Allawi said, arguing that Maliki was courting his Shiite Muslim base by pushing for the trial of Vice President Tareq al-Hashemi, a Sunni, among other moves.

Hashemi was sentenced in absentia on September 9 to death for the murder of a lawyer and a brigadier general. He has insisted charges he ran a death squad are politically motivated.

"Definitely, it can help him to a certain extent in the next election," the former minister acknowledged, but added: "In the long run ... this is not the right way how to govern a country."

"This is the best way for him to stay in power."