Supporters of President Karzai are preparing to rig voting in next week’s presidential elections in unstable parts of Afghanistan’s south as Taleban violence threatens to intimidate voters and hit turnout in his traditional support base.

The Times has talked to several witnesses whose reports will bolster suspicions within the international community that there will be electoral fraud across the south, some of it allegedly orchestrated by Mr Karzai’s half-brother, Ahmed Wali Karzai.

Such irregularities could threaten the credibility of the election process and have led to threats of violent demonstrations in the north if Mr Karzai is thought to have stolen the vote.

Several tribal leaders and local people in Helmand described a systematic attempt by supporters of Mr Karzai to collect or buy voter registration cards from local people.

One tribal elder in the Marja district of Helmand alleged that the vote rigging was being organised by members of Mr Karzai’s family and local tribal allies, particularly Sher Mohammad Akhundzada, the former governor of the province.

“In Marja and other districts we can’t vote because of security problems,” he said. “We are continuing to buy the cards. I am one of the people responsible for collecting cards in Marja. We bought the cards for $30 (£18).”

The man, who asked not to be identified, said that other elders were also collecting cards for Mr Karzai.

“Behind the curtain it is the brother of Mr Karzai and Sher Mohammad Akhundzada who are working on this,” he added.

Wali Karzai and Mr Akhundzada have been accused frequently of involvement in drugs smuggling by Western officials.

Wali Karzai, who firmly denies the narcotics allegations, is the head of the provincial council of Kandahar province and Mr Akhundzada is a member of the Upper House of the Afghan parliament. Neither could be reached for comment.

Another tribal elder in Marja said: “The tribal elders in all the districts are organising this. They buy the voting cards for money or mobile phone scratch cards.”

Threats from the Taleban meant that few people in outlying districts of the province would be able to vote, he said. British military commanders insisted that 90 per cent of Helmand’s population would have access to polling stations but there is no Afghan government presence in five of the thirteen districts in Helmand.

British forces have spent the past month attempting to clear the populous Nad Ali district of Taleban fighters before the elections. Ten British troops were killed in Operation Panther’s Claw, with a total of 22 operational deaths in July.

Haji Mohammad, from Marja, said that he sold all his family’s voting cards because there were no polling stations in his area. He said that he did not want Abdullah Abdullah, Mr Karzai’s main rival, to win.

“I don’t think most of the districts will vote in the election,” he said. “When this team goes to other districts they will buy many votes because everyone is poor, everyone needs money and they can sell their votes.

“When they came to me they said, ‘If you don’t vote then Dr Abdullah will win’. That is why people think it is a good reason to sell their votes. We want Karzai to win the elections.”

Alex Strick van Linschoten, a research analyst in Kandahar, said that there were reports of similar schemes in several districts including Zarai, Panjwai and Maiwand, with local police participating in the process.

The Afghan Independent Election Commission has accredited 160,000 observers to attend polling stations. However, the country’s main monitoring agency, the Afghan Free and Fair Elections Foundation, said that it would have observers at only 70 per cent of stations because of security concerns.

Western diplomats said that precautions designed to prevent fraud would be ineffective in insecure districts of the south, where election monitors could not go.

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