When the Conservative candidate Eshaq Khan unexpectedly unseated a long-serving Labour councillor in local elections last May, it seemed to be the high point of a long career of public service.

He already held senior posts in charitable and cultural groups and was a respected figure in the tight-knit Kashmiri community in Slough, Berkshire, where he ran a carpet and furniture business.

But within days of his triumph, his victory began to unravel amid a welter of allegations of a crude campaign of vote-rigging and, ultimately, forgery and intimidation of a witness.

It ended in disgrace yesterday when Khan was found guilty at a special High Court election hearing in Slough council chamber of corrupt and illegal practices to secure his election. He was stripped of his seat and banned from standing for office for five years. He now faces a police inquiry.

Khan, 50, won his marginal seat in Central Ward after his team registered hundreds of “ghost voters” in the month before the election and cast votes using fraudulent postal ballots.

He and his team compounded the fraud with a botched cover-up that included poorly forged tenancy agreements and statements from bogus voters, and an attempt to intimidate a witness. Thames Valley Police said that it would widen its inquiry into the case in light of the judge’s accusations of perjury and attempts to pervert the court of justice by supporters of Khan.

Three people have been arrested in connection with the case. Police have interviewed another three. The Times understands that they include Khan and a leading figure in his campaign, Mohammed Basharat Khan.

The election team registered fictitious voters at derelict houses and claimed that as many as 12 voters were living at two-bedroom flats or three-bedroom houses. Khan beat Lydia Simmons, his Labour opponent, by 120 votes but Labour contested the result by bringing an election petition to overturn the result after almost 450 voters were added to the electoral register in the final weeks before the poll, almost all of whom voted by post for the Conservatives.

Labour succeeded in striking 145 “ghost voters” from the electoral roll. The judge accepted that the true figure was likely to run into hundreds.

Witnesses included a handwriting expert, Kim Hughes, who said that 198 of the postal ballot forms were filled in by Mohammed Basharat Khan, described by the judge as “a serial forger”, and another 79 were in the handwriting of the candidate.

Once Labour began to identify ghost voters, Khan and his team produced forged tenancy agreements. Ten of these were produced on the same computer. Khan’s team also produced 46 statements by individuals claiming that they lived at the disputed properties.

Two Polish women were accused of lying by Khan’s allies when they said that they knew nothing of the six and seven Kasmiri voters registered at each of their homes. One witness, Nighat Khan, who was due to give evidence that the five Kashmiris registered at her flat were fictitious, received a visit from a man claiming to be a lawyer. He produced a typed letter that he asked her to sign, saying that she would then not have to attend the hearing. The court received a letter allegedly from Ms Khan claiming that she was too ill to attend.

Khan will be forced to repay to Slough Borough Council all the expenses for council duties he claimed since his election and was told to pay aggravated legal costs, although local Conservatives said that some of these may be covered by insurance.

Times Recommends

• Fern Britton: 'I still can't see that I was wrong'
• Extreme cooking
• Easy French: Tarte Tatin