According to claims made against him in an election petition, groups of people were paid to gather outside polling stations and persuade voters to back Lutfur Rahman on election day last month in Tower Hamlets area of east London.
The 49-year-old Bangladesh-born mayor's supporters are accused of canvassing inside polling stations and accompanying voters to booths where they left election material asking people to vote for him, the petition adds.
According to a report in 'The Times', Rahman and his team are also accused of casting postal and other votes in the names of people who were not entitled to be on the electoral roll, and acquired voting papers that they completed in favour of the mayor.
Rahman, an independent social democrat, was the first directly elected mayor of Tower Hamlets in 2010, winning 52 per cent of the vote.
Last month he won a re-election in a closer contest, where he received 43 per cent of first-preference votes but beat Labour party by 37,000 to 34,000 votes when second preferences were included.
If the petition is successful, the mayor faces a rerun of the poll. He could be banned from holding office if the High Court finds evidence of electoral malpractice by him.