Democratic Republic of Congo should renegotiate its $6 billion infrastructure-for-minerals deal with Chinese investors, according to the draft of a report commissioned by a global anti-corruption body of governments, companies and activists.

The draft, seen by Reuters, describes the deal that was first signed in 2008 as "unconscionable" and urges Congo's government to cancel an amendment signed secretly in 2017 that sped up payments to Chinese mining investors and slowed reimbursements of investment in infrastructure.

The final report is expected to be released this month by the Extractive Industries Transparency Initiative (EITI), which tracks revenue flows in the oil and mining sectors and counts more than 50 countries, including Congo, as members.

The report has no legal force but, if the draft's main conclusions remain, it could bolster Congo's push to secure more favourable terms from mining contracts with Chinese investors. 

President Felix Tshisekedi's government is reviewing the 2008 contract and the reserve levels at China Molybdenum's (603993.SS) Tenke Fungurume mine after saying Congo was not getting a fair deal.

Prime Minister Sama Lukonde Kyenge told a mining conference on Thursday: "There has to be some adjustment."

The moves represent rare pushback by Congo, the world's leading producer of the battery metal cobalt and Africa's top copper miner, against the Chinese investors who control most of its mining industry.

Under the 2008 deal struck with the government of former President Joseph Kabila, Chinese state-owned firms Sinohydro Corp (SINOH.UL) and China Railway Group Limited agreed to build roads and hospitals financed by profits from Congo's Sicomines cobalt and copper joint venture.

Critics say few of those projects have been realised.

Congo's government spokesman said he had not read the draft and could not comment. EITI's office in Congo referred Reuters to the terms of reference of the mission and declined to comment further. A Sicomines representative did not respond to requests for comment.

China Railway had no immediate comment. Sinohydro did not respond to a request for comment.

Fred Zhang, a senior Sicomines official, defended the deal in comments to Reuters last week, saying it had driven development for Congo's people and Sicomines would disburse more funds as production rose.