Paul Wiffen, who is campaigning to be MP for Ilford South in east London, responded to a criticism of the party on the Community Care site.
The remarks focused on Muslims, Romanian Gypsies and African and Caribbean communities.
UKIP said he had been suspended but, following his apology and an inquiry, he was allowed back into the party.
The comment was made in response to a post by Community Care's Outside Left blogger on asylum.
Mr Wiffen, chair of UKIP London, said: "You left-wing scum are all the same, wanting to hand our birthright to Romanian gypsies who beat their wives and children into begging and stealing money they can gamble with, Muslim nutters who want to kill us and put us under medieval Sharia law, the same Africans who sold their Afro-Caribbean brothers into a slavery that Britain was first to abolish (but you still want to apologize for!)"
He has since apologised saying: "I was very surprised to see such a party political piece on a website called 'Community Care', and when I read the lies about UKIP being a racist party, I just saw red, and fired off an angry email.
"I am truly sorry to anyone offended by some of the language I used."
A spokesman for UKIP said: "UKIP is a party of real people, not career politicians.
"Real people sometimes make mistakes, and when they do, they should apologise.
"Both UKIP and Mr Wiffen have apologised for any offence caused."
Mike Gapes, Labour MP for Ilford South, said: "There is an unpleasant whiff about Mr Wiffen."
Toby Boutle, the Conservative candidate for the area, said if Mr Wiffen 's comments are correct then "it says a lot about UKIP that someone like this is their regional chairman in London".
Lib Dem candidate Anood Al-Samerai said: "I would not wish to see this man standing in Ilford South."
BBC News
