The blindfolded man, who identified himself as Colonel Ryad Kateh Olyway, was shot in the head by a masked gunman after confessing to collaboration with American forces. Followers of Abu Musab al-Zarqawi, an al-Qaeda-linked militant, claimed responsibility.

The video showed the hostage confessing his supposed crimes as he sat, with his hands tied behind him, on a chair in front of a banner bearing the name of al- Zarqawi’s organisation. He was flanked by two masked men holding assault rifles.

“I worked at the Interior Ministry to collaborate with the American forces,” he told the camera in an expressionless voice. “I gave the names and addresses of fellow officers in the former army, who are Sunnis.

“I saw terrible things at the Ministry of Interior — many Iraqi female prisoners subjected to various kinds of torture, humiliation and harm to their honour. I also spied on other ministries for the Interior Ministry.

“I am very sorry for what I did and I urge my fellow officers at the Interior Ministry to know that the right will undoubtedly come to them (sic).”

Another masked man then read out his sentence. “The religious court of the organisation of al-Qaeda of jihad in the land of two rivers has decided to implement God’s order on this infidel to serve as a lesson to others,” he stated.

Then he killed his captive with a shot to the head.

An Interior Ministry official later confirmed that Colonel Olyway had been kidnapped a month ago by an unknown group.

Al-Zarqawi’s followers have been responsible for the killings of several foreign hostages, including Ken Bigley, the British engineer who was beheaded by a masked man believed to have been al-Zarqawi.

Several Iraqis have been kidnapped and killed for “collaborating” with American and Iraqi security forces, but the “confessional” nature of the video was a departure.

It follows the success of the Interior Ministry’s latest propaganda project — a television show called Terror in the Grip of Justice, which purports to show the confessions of insurgents captured by the ministry’s anti-terrorist commando unit.

The programmes show alleged insurgents, many sporting severe bruises, confessing not only to attacks but also to such un-Islamic activities as drinking and homosexuality.The Interior Ministry cites the show’s popularity as evidence that ordinary Iraqis reject the insurgency and claims that it has encouraged people to come forward with information.

In his confession, the colonel also said that the ministry, a former preserve of Saddam Hussein’s ruling Sunni elite, was now dominated by the long-oppressed Shias and Kurds. Both groups have been the targets of insurgents, particularly al-Zarqawi’s group, in an attempt to rally Sunni support and ignite a civil war.

The video was released amid a political vacuum that has been caused by the failure of Iraq’s leaders to form a coalition government nearly two months after the country’s general election.

Ethnic and religious groups are arguing over the division of ministries, the rights of the Kurdish minority and the role of Islam. The new parliament was expected to convene on Saturday to appoint a government, but failed to do so. It may try again tomorrow.

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