Twenty-three year old William Petzäll has told the tabloid Expressen that he leaves the party because of his addiction problems. But, he says, he'd like to stay on as an MP and work with a subject close to his heart - better help for young alcoholics and drug addicts.
The Sweden Democrat Party leadership "regrets" his decision to cling to his seat, and says that it hopes he will do what is right with respect to himself as well as the voters - and focus his energy on a long-term solution to his problems.
Petzäll took a time-out from politics in February this year, after a drunken brawl resulted in him being taken into custody. According to the party, he relapsed into substance abuse this summer.
Petzäll has spent the last month in a rehab clinic, undergoing treatment for addicts.
According to the conservative Moderate Party, they were approached in August by Petzäll, who said he was considering leaving the Sweden Democrats. Johan Elmberg, press spokesperson for the Moderate party, tells the news agency TT that they want nothing to do with Petzäll: "He has been elected on a Sweden Democrat mandate and we do not share his views."