The Independent has learned from an Iraqi source that the leader of the plot was Ra'ad al-Hazaa, a former army officer in his thirties who is the nephew of General Omar al-Hazaa. The general was a member of the same clan as President Saddam and was executed on his orders in 1990.
The ambush of Uday, one of the most important members of the regime, took place on 12 December, as the President's son was driving with his girl friend in Baghdad.
Ra'ad was formerly an officer in the palace guards. When his uncle was killed he was dismissed. But he was able to gain intelligence of Uday's movements because he was a member of the ruling elite.
Along with four or five others involved in the plot Ra'ad is now in Iran. Iraq has officially demanded they be handed over, but Iran denies their presence.
Uday, 32, remains in hospital in Baghdad, paralysed by at least four bullet wound. One is lodged in his spine, according to opposition groups. The seriousness of his injuries was confirmed by the French government's admission last week that he had been seen by a team of French doctors in Baghdad. Paris has refused permission for Uday to come to France for medical treatment.
If Uday is paralysed, his brother, Qusai, the head of the security services, becomes the heir apparent.
Credit for Uday's ambush was previously claimed by al-Dawa, an extreme Shia Muslim militant movement with a history of attacking Iraqi leaders.
An Iraqi familiar with the events surrounding the attack says: "Al-Dawa were involved in the logistics and knew what was happening. There have always been Shia willing to die to assassinate leading members of the regime. But they never had access to the intelligence you would need to be successful. The Hazaa family, as part of the elite, could provide this."
The origins of the feud which led to the assassination attempt lie in the bloodthirsty politics of President Saddam's extended family. They come from the Sunni Muslim heartland of Tikrit, a city on the Tigris, north of Baghdad. Iraq's ruling circle is known as "the Tikritis." From the 1970s General Hazaa was a divisional commander in the army. But when President Saddam attacked Iran in 1980, General Hazaa became critical of the regime. He left the army and spent much of his time in the retired army officer's club in the Yarmuk district of Baghdad where he had his house.
He is said by other officers to have expressed contempt for President Saddam's branch of the clan, which comes from the village of al-Ouja, just outside Tikrit, and was not part of the clan's traditional leadership.
An Iraqi army officer now in exile says General Hazaa often criticised the President. He says: "In 1990 the general was arrested. He was taken to al-Ouja and his tongue was cut out. Then he was executed. His son Farouq was killed at the same time and the general's house in Baghdad was bulldozed."
The mutilation of political prisoners before execution is common in Iraq as a way of intimidating relatives to whom the body is returned.
Uday is not known to have taken part in the killing but is notorious as the most violent member of the regime. He beat his father's personal bodyguard, Kamil Hussein Jajo, to death in 1988. He also precipitated the flight of General Hussein Kamil, President Saddam's son-in-law, in 1995, and murdered him on his return last year.
Ra'ad and a number of other gunmen waited for Uday near the racecourse in the wealthy al-Mansur district of Baghdad on 12 December. They are said by an Iraqi source to have received information about his whereabouts from "Lubna", a girl with him the car. There are conflicting reports that she was killed or wounded in the attack.
After the ambush, the most successful assault on President Saddam's inner family ever carried out, the attackers fled to Iran, though Iran had no prior knowledge of the assassination. The Iraqi Foreign Minister demanded through the UN Security Council that they be handed over. Iran denied it knew anything about them. The attackers feared Iran might return them to Baghdad and gave information to friends abroad about their predicament.
The attack is a blow to the regime, as it marks the first time that members of the President's clan have co-operated with Shia militants.
It comes just as the regime appeared to be growing stronger, after its successful military intervention in Kurdistan and the limited resumption of Iraqi oil exports.