A rigged election? The latest chapter in Congo's sad history

There are serious concerns over the prospects for fair elections in the Democratic Republic of Congo (DRC) after a confidential report suggested that the register of voters has been manipulated to favour the incumbent, Joseph Kabila.

The historic 28 November polls, only the second vote since the end of a disastrous war in 2003, are seen as crucial to international efforts to prop up a resource-rich country the size of western Europe. But there are serious flaws in the electoral roll including hundreds of thousands of ghost voters, shows an unpublished survey by a Belgian firm on behalf of the Congolese government.

The document, obtained by The Independent, highlights how numerous "duplicates" – voters registered twice – could potentially skew the result to favour re-election of President Kabila.

"For the provinces of Bandundu, Equateur, and Province Orientale, there are a very significant number of duplicates, above what would be expected from the census data," the report concludes. In the province of Kinshasa, a stronghold of opposition leader Étienne Tshisekedi , "the number appears to be normal", it says.

The research was handed to authorities in August by Zetes, a Belgian firm contracted by the government to issue biometric voter cards. Rumours of its contents in DRC have since prompted accusations of vote-rigging, but the government has rejected any accusations of irregularities with the electoral roll and has refused opposition demands to release the report or to allow an audit of the apparently flawed database.

Some duplicates could be attributable to technical glitches, but Zetes appears to suggest tampering is a more likely explanation due to the scale. "This leads one to think that it amounts to a direct manipulation," the report says.

In several of the Congolese provinces, the double entries are equivalent to more than 12 per cent of voters. The margin of error for duplicates on similar databases used in Western elections is less than 1 per cent.

Preparations for the vote on 28 November, in a vast country with few roads and little infrastructure, have been dogged by serious delays. Even as campaigning officially began yesterday, ballot boxes and other materials have yet to reach most of the 62,000 polling stations across the country. Senior figures in the UN mission in Congo (Monuc) said last month that it would be "impossible" for the presidential and parliamentary polls to happen on time.

Western donors have pumped more than $1bn into state-building efforts in a country still hobbled by armed insurgencies fuelled by the illegal minerals and timber trades. The UN is backing logistical efforts for the November vote with more than $100m. Donors are footing a further $210m in election costs, while continuing to supply half of the country's $6bn annual budget.

This year, Mr Kabila controversially changed the law to scrap a second round in the presidential vote in what was seen as an effort to improve his own chances of winning a single vote against a fragmented opposition.

"Who are we investing all this money for?" asked Congo analyst Jason Stearns. "Are we investing all this money for a rich elite to stay in power in Kinshasa? It's no good donors wringing their hands over the state of the army, the judiciary or the police. Elections are the chance to hold leaders accountable for the state of institutions."

So far diplomats and Western governments – some of whom have seen the Zetes report – have been wary of criticising the Kabila administration or the electoral process. "It's important for us to build up a climate of trust and not mistrust," said Manuel Lopez Blanco, director for West and Central Africa in the EU's external action service. "We must not build up a list of reasons as to why the elections won't work. Otherwise it will become a self-fulfilling prophecy."

More than four million people are thought to have died as the result of recent wars in DR Congo. The legacy of the former dictator, Mobutu Sese Seko, who looted the country for 32 years, and Laurent Kabila and his son, Joseph, who have ruled since is a country synonymous with rape, atrocities and corruption. A patchwork of armed groups, including Rwandese former genocidaire and the quasi-religious Lords Resistance Army, still terrorise large areas, and the Congolese army is regularly accused of appalling human rights abuses.

Tensions are already mounting on the ground, with clashes between government and opposition supporters in the capital Kinshasa in recent weeks. An opposition television station was among a number of buildings burnt to the ground in September, with many people fearing a prolonged standoff after the vote.

"This election in Congo is the ultimate test," said Thierry Vircoulon, from the International Crisis Group. "Is Congo on course to consolidate its fledgling democracy or return to a state of widespread instability, insecurity and violence?"

In the ballot box: The main candidates

Joseph Kabila

Joseph Kabila was never expected to stay in power. He was only 29 when he took over from his assassinated father, Laurent, and had to survive at least two attempted coups before he won an election in 2006. He cut his teeth as a commander of a brigade of child soldiers in his father's army during the Rwanda-backed war against the Mobutu regime. Educated in Tanzania, Uganda –and later China – he was seen by many in the Democratic Republic of Congo (DRC) as an outsider. His main support at the last election came from the east, where he was born, but discontent at the lack of a peace dividend has eroded his backing in all parts of the country.

Étienne Tshisekedi

Tshisekedi, 78, is the nearly man of Congolese politics, a perennial opposition figurehead who has always lost out on the top job. Thought to see next month's elections as his best chance, Tshisekedi spent three stints as prime minister to Mobutu Sese Seko, the first of which lasted a month and the third a week, as rebels approached the capital. He boycotted the last elections contested by Joseph Kabila and alleged warlord Jean Pierre Bemba, who is now on trial for war crimes. He has been accused of being obsessed with the constitution he helped edit in 1967.

Vital Kamerhe

Vital Kamerhe is expected to come third in a packed presidential field. Accused of being a Mobutu supporter in his youth, he later joined the main opposition UDPS and then served under President Kabila before setting up his own party. Still seen as "the kid" by the veteran opposition leader Étienne Tshisekedi, it was hoped the two men would make a united stand against President Kabila. He is backed by the rich and influential Jean Pierre Bemba, the runner-up at the last election now on trial for war crimes at the International Criminal Court in the Hague.