Councillor Frank Ward has announced he is leaving the Labour Party and will stand as an independent candidate for Kenilworth ward, Borehamwood, in May.
Mr Ward failed his party's selection process to represent Labour in the seat which he has held for 24 years, but refused to confirm whether he would stand as an independent until nominations closed this week.
He has accused members of Hertsmere Labour group of discrimination and a conspiracy, claiming he was once called a religious fanatic' at a party meeting.
A spokesman for Hertsmere Labour group said: "It was the view of the Labour Party that he failed to meet the required standards to be considered as a Labour Party candidate. Subsequently it was his decision to remove himself from the selection process."