Bodil Schibli, who was a lay judge in Ystad District Court until February, wrote several letters to Reinfeldt imploring the government to "protect its own people" against "these fanatical immigrants, who really have no reason to be here, other than to be supported by taxpayers."
According to Skånska Dagbladet, she also wrote that Islam should be "forbidden from further spreading itself in our country."
Schibli sat on panels which passed judgements in a number of cases involving immigrants, including twelve cases in 2007.
Judge Ralf G Larsson, head of Ystad District Court, said it was unsuitable for a lay judge to write letters such as those written by Schibli.
"If this had come to my attention when she was still a lay judge, I would have had a serious talk with her," he told Skånska Dagbladet. Schibli resigned after falling asleep during a trial earlier this year.
Contacted by the paper on Thursday, Schibli was unrepentant. She insisted that she had always judged according to the law, not her own opinions. She also claimed that 90 percent of lay judges in Sweden shared her views.
"There has never been a multicultural society that worked - only in the minds of politicians," she said.