Employees of Tower Hamlets Council were warned they may lose their jobs if they did not each illegally obtain 100 votes for Mayor Lutfur Rahman, according to court documents seen by BBC London.
Mayor Rahman and his party face claims of corrupt practices and exerting undue spiritual influence on voters.
A file obtained by the BBC now provides a raft of detail on the allegations Mr Rahman faces in court next month.
The mayor and his party Tower Hamlets First deny any wrongdoing.
The evidence will be heard over several weeks at the High Court by Richard Mawrey QC. He has the power to order a recount or ban the mayor from public office for up to five years.
Part of the Statement of Case, collated by the members of the public who brought the legal action, details an array of alleged misdeeds in the run-up to the election last May, when he was re-elected as mayor.
It claims that in April last year, 30 council employees were asked to a meeting at a Bangladeshi restaurant.
The document continues: "During the meeting both council managers and agents of the First Respondent [Mayor Rahman] instructed each of those attending to obtain 100 votes each for the First Respondent; and informed them that, if they did not do so, they may lose their jobs.
"It was made clear that these votes should be obtained by illegal means, including through postal voting fraud."
The petitioners allege that at another restaurant meeting in the period: "The First Respondent attended together with all or almost all the Tower Hamlets First candidates for the Council elections and some activists.
"The First Respondent told all assembled activists that they must fill up to 250 postal vote application forms each. More
