Michael Hardern, a publicity-seeking former butler, walked into a branch of the Britannia Building Society in Kingsway, London, yesterday and passed a handwritten note over the counter.
The note signalled his intention to withdraw from elections to the board of directors. It arrived just four days before the deadline for voting forms to be returned.
In December Mr Hardern collected over 50 nominations to stand for election via an Internet website for carpetbaggers.
Britannia says it has already spent pounds 2.2m on holding a contested election.
The society yesterday said it was studying the note. If it is legally valid as a withdrawal, the current voting form is inaccurate and Britannia must re-ballot its members.
It must also hold a second general meeting to assess the vote.
A spokeswoman for the society said a full statement would be made tomorrow, after legal advisers had reported.
Mr Hardern blamed the society for his withdrawal. "I didn't stand a chance because of the way the ballot was rigged.
"If they have to hold another ballot that's their fault. They should have run an honest, decent, non-Banana-republic Serbian vote. Do you want me to say that again?"
He said this was "not the end of the line". He was still promoting a proposal to de-mutualise West Bromwich Building Society, to be debated this summer.