Moves to cancel Mr Fogerty's membership had come too late, he said.
He did not want to be a part of a group that had not "done their homework" on its members.
"I've now decided to withdraw from the organisation. I wish to have nothing to do with anyone that holds those views."
Mr Harvey said he still had serious concerns about MMP, which he claimed had provided a vehicle for "failed politicians" to stay in parliament through the party list.
"I haven't lost my passion for the subject.
"I still believe that MMP has failed and this country should be looking at it again."
Vote for Change, which was launched recently to advocate a change from MMP, said yesterday it was investigating the allegations against Mr Fogerty.
"The allegations of Mr Fogerty's previous membership of a white supremacist group appear to be true and he will be asked to resign his membership immediately, or have his membership revoked if he chooses not to resign.
"Vote for Change will not be commenting on this unfortunate matter further."
Mr Fogerty's name was deleted from the Vote for Change website yesterday.
Anti-race hate site "Fight dem back" has highlighted what it called the "extreme" views of Mr Fogerty from 2005.
In emails, Mr Fogerty angrily suggested someone harm Darp Hau, a promoter of racial harmony.
"What a tosser, someone should put a few bullets into the glass to give him a scare which will also give him some time to think about cleaning up his act while he cleans up the glass," Mr Fogerty wrote.
"How much does murder go for these days? Maybe his 'accident' should be by running into two well-paid abos.
"I would like to hang him high, not swear at him.
"Where does he live in Sydney? He in the phone book? He shames our good Kiwi name (LOL)."
