An investigation commissioned by the South African government into the UN oil-for-food programme in Iraq cleared Deputy President Kgalema Motlanthe of corruption, a report released Wednesday said.

The probe was ordered by then president Thabo Mbeki in 2006, into what has become known in the country as "Oilgate," to look at allegations of kickbacks sourced by senior members of the ruling party from the State Oil Marketing Organisation of Iraq (SOMO).

"The content of the June report exonerated Mr Motlanthe of any liability in relation to the payment of oil surchages," the report said.

Motlanthe, not in government at the time but secretary general of the ruling party African National Congress (ANC), was implicated in the shady dealings with SOMO.

The leading businessman and current minister of housing Tokyo Sexwale was also cleared in the investigation.

"Mr Sexwale was exonerated from liability as a participant in illicit activities ... it was reiterated that participation in the program by South African entities was characterised by compelling indications of exploitation by foreign entrepreneurs."

The UN oil-for-food programme ran from 1996 until 2003, when US-led forces invaded Iraq.

It allowed Baghdad to sell limited amounts of oil to fund UN-supervised imports of humanitarian goods which the country lacked because of tight UN sanctions imposed after Iraq's invasion of Kuwait in 1990.

The report was kept secret since its completion in 2006.

"Former president Mbeki decided against releasing the report pending the advice from the chief state law adviser and due to its incompleteness among other reasons," President Jacob Zuma's spokesman Mac Maharaj said.

Zuma announced in October he would release the report, sparking speculation he wanted to incriminate Motlanthe and Sexwale, who are seen to be his rivals for the ruling party's top position in two years.

Maharaj stressed that the report does not make "any definitive final findings in respect of the conduct of the named individuals in so far as the impact of such conduct on UN resolutions and policy is concerned".