"When I was 17, I was actually driving a car and I did kill someone," Jonathan Bartley admitted to talkRADIO's James Whale.
In an interview on Monday night, the Green Party co-leader opened up about the accident live on air.
"I was coming back from a gig and a guy came out in front of me and I killed him, and I've had to live with that for the rest of my life," he said.
"I grew up with a strong moral code and it felt as though I had been responsible by mistake... I felt so low."
Bartley said his faith, along with good friends and family, helped him through.
He also talked about the time he met the family of the man.
"I wasn't sure whether to go up to them or not... I can't imagine what it must have been like," he said.
"I was at that place where I would have done anything to make things right again."