Poll rigging, sex jibes and a case of the Oxford blues at prestigious university's union

Five British prime ministers, from Gladstone to Heath, were officers of the university debating society while former Pakistan leader Benazir Bhutto, assassinated last month, was once its president.

In recent weeks, however, the 185-year-old union has been overtaken by a political scandal involving those very modern subjects of electoral malpractice, sex and money.

The latest winner of the vote for president, Krishna Omkar, has been disqualified from office for breaking the union's strict rules over campaigning.

A fresh poll was ordered to find a replacement and Charlotte Fischer, his beaten opponent, was expected to win this time.

But she has walked out of the contest and the university, returning home in distress after claiming that union officers sent her texts asking: "Fancy a f***?".

Such communications are expressly barred by rule D3(c) of the union's lengthy code of conduct, which "prohibits the use of any swearword or slang of a sexual or scatalogical nature".

"I resigned because I was so fed up with personal attacks," said the 20-year-old at her family's £750,000 home in Orpington, Kent.

"The texts were from two or three people I was not on friendly terms with. I told them I was unhappy about it, but it carried on. I'm just exhausted."

Strife began to tear the union late last year after Mr Omkar, 23, who is studying for a PhD in sociology at Merton College, won the presidential poll.

Miss Fischer, studying modern history and politics at Balliol College, formally complained that her opponent had broken election rules.

She claimed that Mr Omkar, from New Delhi, invited supporters to a meeting and sent e-mails soliciting votes - both banned practices.

At a series of lengthy tribunal hearings, Mr Omkar claimed his meeting was simply a party - but the tribunal report noted that "no alcohol was present. This was not a party".

In a ruling which condemned Mr Omkar as "arrogant" and a "brash newcomer to the university", he was stripped of the right to the presidency, which he was due to take up next term, and, uniquely, banned from ever running again.

But his supporters complained that Miss Fischer had unfairly brought in a London barrister to represent her, and there were whispers that she was a member of the wealthy Rothschild banking dynasty.

This week Miss Fischer left her college rooms after arranging to continue her degree in a year.

In an astonishing 3,000-word resignation letter, she said: "I have continued to receive text and Facebook messages from several members of the union asking if I 'fancy a f***?'

"When I called the member whose phone the messages were sent from, I received no answer, only further messages asking me if 'that was an offer of phone sex, gorgeous?'

"It was insensitive at best and outrageously obnoxious at worst."

Miss Fischer is a former pupil at the state girls' grammar school Newstead Wood in Orpington.

Her father Martin is an author and senior fellow at the King's Fund health think tank. Her mother Sylvia's madien name was Rothschild.

"The union is very pompous for a student society and has incredibly complex rules," she added.

"But I did not pay for a barrister - he was a family friend. And I am not a member of the Rothschild banking dynasty."

The current holder of the presidency, which changes every term, is Emily Partington, 20, of Jesus College.

She said diplomatically: "Charlotte wrote her letter of resignation from a personal point of view."

Mr Omkar was last night appearing in a student production of the play Edward II, in which a rightful leader is brutally despatched by his enemies.

He did not respond to requests for comment, but suggested in an earlier statement that Miss Fischer had brought "mistrust and hate" upon herself, and demanded the right to put himself forward in another election.