The British National Party candidate for Waddon was questioned by police over possible election fraud in 2006.
Charlotte Lewis stood in the May elections for a ward in Sutton, despite living in Thornton Heath.
Electoral rules dictate candidates must live or work in the borough they intend to represent, but Miss Lewis did neither.
She had placed on her nomination form an address in Lind Road, Sutton, as her home residence – only for a London newspaper to expose the address as false.
Miss Lewis claimed she was in a relationship with a resident at that address at the time but admitted she did not live there full time.
Speaking ahead of the Waddon byelection, Miss Lewis said she had been “taken advantage of” by a party organiser who has since left the organisation.
She said: “It was down to the previous branch organiser.
“There was a guy who lived in Sutton who was supposed to stand but he disappeared. I was drafted in at the last minute.
“I very much regret what happened in 2006. I was taken advantage of and it won’t happen again.
“I am wiser and that person who cannot be trusted has gone.”
The 36-year-old said she had got confused as the Greater London Assembly constituency combines both Croydon and Sutton.
She added: “I did not have time to familiarise myself with electoral law.”
Miss Lewis was questioned by the police at the time but the incident was not taken up by the electoral commission, nor the local council, and no charges were brought against her.